
Class .^ROiii 
Book ■ HS ~ 



Copyright N?. 



CBEflilGHT UEPOSIC 



' 



CARRIERS 

IN 

INFECTIOUS DISEASES 



A MANUAL ON THE IMPORTANCE, PATHOLOGY, DIAGNOSIS 
AND TREATMENT OF HUMAN CARRIERS 



BY 

HENRY J. NICHOLS, M.D., M.A. 

Major, Medical Corps, U. S. Army; Instructor in Bacteriology, 

Parasitology and Preventive Medicine, Army Medical 

School, Washington, D. C. 



WITH 

A SECTION ON 

CARRIERS IN VETERINARY MEDICINE 

BY 

R. A. KELSER, D.V.M., M.A. 

Captain, Veterinary Corps, U. S. Army; 

In Charge, Veterinary Laboratory, Army Medical School, 

Washington, D. C. 



BALTIMORE 

WILLIAMS & WILKINS COMPANY 

1922 



It' 






COPTEIGHT 1922 

WILLIAMS & WILKINS COMPANY 

Made in United States of America 



All rights reserved, including that of translation into foreign languages, 
including the Scandinavian 



ICI.A6868 1 7 



COMPOSED AND PRINTED AT THE 

WAVERLY PRESS 

Bt the Williamb & Wilkins Compaky 

Baltimore, Mo., U. S. A. 



^V 15 /oc 



1322 
vie i 






To 

The Spirit of Science 

and 
The Instinct of Service 



PREFACE 

In writing this book, the author has attempted to prepare a 
manual on that young but rapidly growing specialty in preventive 
medicine, which, for want of a better term, may be called carrier 
work. The subject has been treated as a part of general medicine 
and surgery, and the book is intended to be of practical value to 
medical students and physicians, especially those with public 
health responsibilities. The didactic or text book method of 
presentation has ; therefore, been adopted, rather than the mono- 
graphic. There are already two monographs on this subject in 
English: "The Carrier Problem in the Infectious Diseases," by 
Ledingham and Arkwright, and "Human Infection Carriers," by 
Simon. The writer's aim is not to compete with these valuable 
works, but to supplement them. No effort is made to develop 
the subject historically or bibliographically, except to emphasize 
certain points or to refer to recent summaries. The idea has been 
to give a systematic exposition of current medical theory and 
practice as relates to carriers. Some idea of the amount of work, 
which has been and is being devoted to this subject, can be gath- 
ered from the fact that there are in the catalogue of the Surgeon- 
General's Library, on typhoid carriers alone, over three hundred 
references to recorded experiences. An effort has been made to 
collect, from these sources and from practical experience, the 
lessons that survive the test of time and trial and thus deserve a 
place in the program for the future. 

The writer has had personal experience with carrier problems 
from several different angles. On the theoretical side, anyone who 
in these days works intelligently for the health of groups, as well 
as of individuals, soon realizes that carriers as well as cases must 
be considered in any rational and radical program for the control 
of the infectious diseases. In attempting to study carriers, it was 
found that animal experimentation afforded a good method of 
approach, as human carriers are not always available when desired 
and clinical conditions often cannot be analyzed experimentally. 



6 PKEFACE 

Some personal experimental work was, therefore, done on the 
mechanism of carrier production, and on the possible use of 
animals in solving carrier problems. On the practical side, it 
has fallen to the author's lot to investigate the origin of several 
epidemics in which the carrier possibility was a proved or unproved 
factor. Considerable laboratory work in the bacteriological 
diagnosis of carriers, the virulence of cultures, etc., has also been 
done in the course of routine duties. Clinically, before and 
especially during the war, I had an opportunity to test the results 
of surgical treatment of typhoid, diphtheria and streptococcus 
carriers and am convinced of the value of these measures. During 
the war, survey and carrier work, which was done on a larger scale 
than ever before, yielded much new information. Many ques- 
tions of policy and feasibility were also raised. Some personal 
experience with such problems has been valuable in orienting the 
subject. Several years' experience in teaching infectious diseases 
at the Army Medical School has also emphasized the importance 
of the subject of carriers in a general course. Altogether, there- 
fore, from personal experience, the author believes that there is 
a place for a practical manual on carriers. The shortcomings of 
this attempt are realized, but it is hoped that these pages may 
assist in a more systematic understanding of the problem and may 
lead to more effective use of our knowledge. 

It is a pleasure as well as an obligation to acknowledge much 
indebtedness to the staff and organization of the Laboratories of 
the Army Medical School, under the Directorship of Lieutenant- 
Colonel Charles F. Craig, and to the Curator of the Army Medical 
Museum, Major G. R. Callender, of the Medical Corps of the 
Army. 

Carriers exist in the infectious diseases of animals and plants as 
well as of man, and the comparative or biological method is as 
valuable in the study of carriers as it is in other branches of 
medicine. In addition, there are, of course, practical carrier 
problems for veterinarians and horticulturists. Plants differ in 
so many respects from man and animals and so little is known 
about their mechanism of immunity, that this field can not be 
discussed here with much advantage. Carriers among animals, 
however, are better understood and are analagous to human 






PREFACE 7 

carriers. In fact, all our animal experimentation is a part of 
veterinary medicine. Moreover, in several of the infectious dis- 
eases, animal carriers directly concern physicians. In order to 
cover this interrelated field, Captain R. A. Kelser, of the Veteri- 
nary Laboratory of the Army Medical School, has contributed a 
section on carriers in veterinary medicine. 

This publication is made with the permission of the Surgeon- 
General, United States Army, who, however, is not responsible for 
any opinion expressed or conclusions reached herein. 



CONTENTS 
Introduction. Definitions 13 

PARTI. GENERAL CONSIDERATIONS 

I. Importance 21 

II. Pathology 25 

III. Diagnosis 34 

IV. Treatment* 37 

PART II. SPECIAL DISEASES 

V. The typhoid fevers 45 

VI. Cholera ' 60 

Vll. The dysenteries 64 

a. Bacillary 64 

b. Protozoal 66 

VIII. Helminthoses 70 

IX. Diphtheria 72 

X. Epidemic meningitis 79 

XI. Pneumococcus pneumonia 87 

XII. Streptococcus infections 90 

XIII. Other respiratory infections 97 

1. Influenza 97 

2. Vincent's angina 98 

3. Tuberculosis 99 

4. Diseases of unknown etiology or due to filterable viruses. 100 

XIV. Blood diseases 101 

1. Malaria 101 

2. Other diseases of the blood 102 

3. Skin diseases 103 

XV. Sexual diseases 104 

1. Syphilis 104 

2. Gonorrhoea 106 

PART III. SUMMARY 

XVI. The relations of phorology to preventive medicine Ill 

1. The place of carrier work in preventive medicine Ill 

2. The method of carrier work 114 

3. Carrier work in the military services 116 

9 



10 CONTENTS 

PART IV. CARRIERS IN VETERINARY MEDICINE 
XVII. Carriers of organisms pathogenic for both man and the lower 

animals 123 

A. Carriers of bacteria 123 

1. Micrococcus melitensis 123 

2. Bacillus tuberculosis 125 

3. Organism of the Salmonella, Enteriditis or Gaertner 

group 129 

4. Bacillus tetani 132 

5. Bacillus oedematis maligni 134 

6. Bacillus anthracis 135 

7. Bacillus mallei 136 

8. Bacillus diphtheriae 137 

9. Bacillus pestis 139 

10. Bacterium tularense 140 

11. Bacillus erysipelatis suis 141 

12. Miscellaneous facultative-pathogenic bacteria 143 

B. Carriers of protozoa 145 

1. Leishmania canis 145 

C. Carriers of filterable viruses 147 

1. Virus of foot-and-mouth disease 147 

XVIII. Carriers of organisms pathogenic for animals and possibly for 

man 151 

A. Carriers of bacteria 151 

1. Streptococcus of infectious mastitis of cattle 151 

2. Bacterium abortus (Bang) 153 

B. Carriers of protozoa 156 

1. Trypanosomes 156 

2. Other protozoal and metazoal infections 159 

XIX. Carriers of organisms pathogenic for lower animals only 161 

A. Carriers of bacteria 161 

1. Bacillus bipolaris septicus 161 

2. Bacillus necrophorus 162 

3. Bacillus paratuberculosis 164 

4. Bacillus pullorum 166 

B. Carriers of protozoa 167 

1. Piroplasma bigeminum and Piroplasma bovis 167 

2. Piroplasma caballi and Nuttallia equi 170 

C. Carriers of filterable viruses 171 

1. The virus of equine infectious anemia 171 

2. The virus of contagious pleuro-pneumonia of cattle . . 173 

3. The virus of equine influenza 175 

4. The virus of hog cholera 176 

XX. Conclusion 177 

Index 183 



CONTENTS 11 

ILLUSTRATIONS 

1. Section of tonsil from diphtheria carrier 27 

2. Section of tonsil showing yeast-like parasite 28 

3. Section of tonsil with crypts injected with lampblack and paraffin. 29 

4. Section of gall bladder of typhoid carrier 31 

5. Section of gall bladder in experimental typhoid carrier in rabbit. 32 

6. Picture of duodenal tube 52 

7. Gall bladder from typhoid carrier who was cured by cholecys- 

tectomy 56 

8. Gall bladder from typhoid carrier who was not cured by cholecys- 

tectomy 57 

9. Kidney from typhoid carrier who was cured by nephrectomy 58 

10. Section of tonsil of diphtheria carrier 75 

11. Section of tonsil of streptococcus carrier 93 



INTRODUCTION 

It is common knowledge that the recognition of the infectious 
nature of many diseases made a new era, both in the theory and 
in the practise of medicine. On the philosophical side, the para- 
sitology of Pasteur and Koch soon became linked up with Darwin's 
grand conceptions and has taken its place in the scheme of the 
struggle for existence and natural selection. On the practical side, 
the "germ theory" has revolutionized medicine by giving us much 
new insight into and control over many diseases. 

Within the realm of the infectious diseases, the concept of the 
so-called healthy carrier was also epoch making. It pointed to 
a new possibility in the outcome of the fight of man against his 
parasites. The patient may recover with complete destruction of 
the parasite. The parasite may win with death or disability of 
the patient. But there may also be a draw with the production 
of a carrier. The appreciation of this possibility lead to fresh 
progress in the explanation and prevention of infections. The 
original observations are accredited to Koch in his work on cholera 
in 1892-1893. Work on typhoid fever developed the subject and 
by degrees carriers have been given a regular place in the picture 
of infectious diseases. Most of our exact knowledge has come 
from work on typhoid and diphtheria carriers. 

It may be accepted that the continued existence of many infec- 
tious diseases depends, to a considerable degree, on the spread of 
pathogenic parasites from apparently healthy and usually immune 
individuals to susceptibles. The strength of the carrier program 
rests on the possibility of detecting such parasites and such sus- 
ceptibles and of keeping them separated. This possibility, how- 
ever, depends on scientific knowledge and on administrative con- 
trol, neither of which is complete. In many diseases we have no 
ready means of determining the virulence of the parasite in the 
possible carrier or the susceptibility of the possible host. In 
addition, when we have this knowledge, it is often impossible to 
apply it practically on a large scale on account of the limitation of 

13 



14 INTRODUCTION 

laboratory facilities and because the affairs of life are not run 
purely for preventive medicine. The carrier program, therefore, 
admittedly has its weak points. However, with the increase of 
the exactness of our knowledge and with the generalization of 
scientific education, social consciousness is calling for more and 
more carrier work. The specialist and the man on the street are 
gradually joining their forces for a strong combined attack on the 
carrier problem. 

The greatest need in carrier work at present is the intelligent 
cooperation of medical men in making a workable synthesis. Too 
often the bacteriologist knows only his germs, the physician knows 
only his patient, and the sanitarian knows only the gross situation 
in the field. Each tries to construct the whole story from his own 
point of view and as a result the literature contains many asser- 
tions, half truths and guesses which hinder real progress. The 
only way to improve is for all concerned to get closer to the reali- 
ties and to cooperate with mutual self-restraint. 

In view of the increasing importance of the subject, a special 
terminology is desirable. The term "bacteriophoria" has been 
proposed to indicate the condition of carrying bacteria. But this 
term does not include the carrying of protozoa and metozoa and 
does not cover the science and art of the subject. A more precise 
word would be parasitophorology, or for short, phorology. A 
carrier would be a phore, or a phorist, and a worker on carriers 
would be a phorologist. While these words might lend them- 
selves to ridiculous developments, such as treponemaphorologist, 
it appears that phorology and phorologist (medically speaking) 
might be useful at times and they are suggested for consideration. 

A carrier is an individual who harbors and transmits pathogenic 
parasites without showing the usual evidences of infection. Some 
carriers show no clinical or pathological evidences at all and are 
really healthy, but the most important carriers are only apparently 
healthy, because, on careful examination, they do show signs or 
symptoms of local infection. Although in some instances the 
parasites are carried purely mechanically, in the worst carriers 
they have a home which is usually a slight chronic inflammatory 
lesion of a mucous membrane. The absence of disease in carriers 
is due to the fact that the carrier either (1) is in the stage of incu- 



INTRODUCTION 15 

bation; (2) has a general but not a local immunity; or (3) is too 
slightly infected to show symptoms. 
Carriers may be classified as follows : 

1. True carriers 

A. Incubationary carriers — temporary 

B. Convalescent carriers — temporary, chronic and 
relapsing 

C. Contact carriers — temporary and chronic, pri- 
mary and secondary. 

2. Pseudo-carriers 

3. Possible carriers 

1. True carriers. The parasites are pathogenic and virulent. 
Questions of relative virulence are of course involved and many of 
them are unsettled at present. The weight of evidence, however, 
is against sudden changes of virulence and in true carriers, accord- 
ing to actual tests or reasonable assumption, the organisms are of 
sufficient virulence to infect. 

A. Incubationary or precocious carriers are infected and infec- 
tive individuals in the incubation period of various diseases. 
These carriers are recognized as especially dangerous in the acute 
exanthemata. They have also been recognized in cerebrospinal 
meningitis, typhoid, cholera, and other diseases. In some car- 
riers the germ apparently has a "resting" period much longer than 
the clinical incubation period. Even with the ordinary period of 
days and weeks, an apparently healthy person may in this way 
spread trouble in many directions. 

B. Convalescent carriers are of three kinds, the temporary, 
chronic and relapsing. 

1. Every case must pass through the temporary convalescent 
carrier stage and fortunately most cases terminate in this way. 
There is a clean-up fight between the body cells and the parasite 
with complete victory for the tissues. Along with convalescence 
or soon afterwards, the patient is disinfected by immune bodies 
and phagocytes and does not infect his environment or immediate 
contacts. 

2. A small percentage of convalescents, however, become 
chronic carriers. These form the bulk of the carrier menace and 
problem. The microorganisms perpetuate themselves from car- 



16 INTRODUCTION 

rier to case and from case to carrier. This is the vicious circle 
which must be broken to win the fight against infectious diseases. 

3. Relapsing carriers. A group of this kind is useful as it covers 
convalescent carriers who later relapse into cases. Examples of 
such carriers are found especially in protozoal infections in which 
the immunity is not as sharp as in bacterial infections. The 
point of difference between a chronic or latent case and a relapsing 
carrier is the slowly progressive nature of the infection in cases and 
a complete balance, even if temporary in carriers. If the carrier 
conception is broadened to include the infection of one organ 
within the individual by a carrier lesion in another organ, cases 
of focal infection can be considered relapsing carriers. 

C. Contact carriers or "healthy" carriers are those who acquire 
the parasite from association with cases or carriers without 
developing the disease themselves. Such carriers are already 
immune. Differential diagnosis between a contact and incuba- 
tionary carrier can be made in most cases only by the outcome. 
Contact carriers are usually temporary, but may become chronic 
if there already exists some predisposing chronic focus. Thus, 
an immune contact carrier with a negative Schick test and an 
obstructed nasal passage may carry diphtheria bacilli until the 
deformity is corrected. Contact carriers may be primary, that is, 
infected by a case, or secondary, infected by another carrier. The 
importance of pure contact carriers has been exaggerated. Many 
so-called contact carriers are really convalescent carriers after 
mild infections, as has recently been emphasized by Craig. 

Contact carriers might include also "mechanical" carriers such 
as surgeons with contaminated hands, but such carriers as well 
as inanimate objects which carry infection by indirect contact 
are best considered under personal hygiene and general sanitation. 
There is nothing distinctive about their carrier relationships. 

2. Pseudo-carriers. A group should be made for carriers of 
non-pathogenic and non-virulent organisms. These may be called 
pseudo-carriers. In any extensive carrier work suspicious organ- 
isms are found which, however, on further examination, turn out 
to be of no importance. In the meantime, the patient may have 
been handled as a true carrier. The diagnosis should be changed 
to that of pseudo-carrier. Such carriers are especially well 
recognized in diphtheria. 



INTRODUCTION 17 

3. Possible carriers. A group of possible carriers may well be 
made to account for the considerable number of persons who carry- 
organisms of uncertain significance. These organisms at present 
can neither be proved nor disproved to be of importance, on ac- 
count of the inadequate state of our knowledge. Under this head- 
ing would come many carriers of streptococci, influenza bacilli, 
and various intestinal organisms. With increasing knowledge 
this group will naturally disappear as the members of it are dis- 
tributed among the true and psuedo-carriers. 

Convalescent carriers have been called active and contact 
carriers, passive. These terms are valuable in emphasizing the 
difference between the active focus of multiplication in convales- 
cent carriers and the usual absence of a home in the contact 
carrier, but they are somewhat misleading as all true carriers are 
active from the point of view of the parasite. 

Cases have also been called acute carriers, but this is believed to 
be an unfortunate use of terms, as it is desirable, on many grounds, 
to distinguish as clearly as possible between cases and carriers. 

Insects which transfer pathogenic microorganisms are often 
called carriers. In malaria, the mosquito is as an essential part 
of the carrier mechanism as the formation of gametes in the 
blood. The final result is also the same, whether typhoid, dysen- 
tery or cholera germs are spread by the fingers of a carrier or by 
the feet of a fly. But the subject of insect carriers, while closely 
related to that of human carriers, practically, deserves separate 
consideration theoretically. 

From the biological point of view, as has already been pointed 
out, the chronic carrier state must be considered as the result of a 
drawn battle between mankind and its parasites. It is personal 
victory as the invader is restricted to an insignificant position; 
it is a social defeat, however, as the invader still main- 
tains a foothold and is able to attack new individuals. In other 
words, chronic carriers are examples of the balance which nature 
tends to establish in the struggle for existence. The same carrier 
balance is seen in the whole scale of life from the lowest to the 
highest forms. Whether in plants, animals or man, parasites are 
competing with hosts in the infectious diseases and the carrier 
state is one end result. Neither side wins a complete victory. 



18 INTRODUCTION 

The situation is compromised and infection and immunity are 
balanced against each other. While we accredit nature with 
marvellous adaptations for the welfare of mankind, it should not 
be forgotten that a typhoid gall bladder or a diphtheria tonsil 
represent a diabolical mechanism for the perpetuation of some 
of man's real enemies. It is the aim of preventive medicine to 
break up this balance in favour of man. 

Work on carriers is another evidence of, and argument for, the 
socialization of medicine. The extreme individualism of the 
past is very satisfactory to the favored few, but it does not take 
into consideration the welfare of the many who make up the 
strength of the nation and who have a way of getting what they 
want and need. The care of the individual case is a unit of 
medical attention, but it is only part of an adequate program for 
the control of infectious diseases. The carrier is also a problem 
which requires special handling, technical and administrative. 
In addition to diagnosing and treating the case, physicians should 
learn to diagnose and treat the carrier and keep pace with the 
increasing social demands for the application of practical measures. 
As physicians and citizens we need to realize, once for all, that 
while in some respects the individual is an ultimate unit, in others, 
he is only a part of higher units, the family, the community, and 
the nation, and he cannot exist without them. Hence, medically 
as well as biologically, the interests of the whole, that is, of the 
race, are greater than those of the individual parts. On the other 
hand, it is the individual who, in the long run, profits from the 
welfare of the group. 

M. G. D.: Brit. Med. Jour., 1917, ii, 633. 

Sacquepee, E. : Les Porteurs de germes. Bulletin de L'Institut Pasteur, 
1910, 8, 1, 321, 689. 

Ledingham and Arkwright: The Carrier Problem in the Infectious 
Diseases. 1912, Edward Arnold, London. 

Simon, C. E. : Human Infection Carriers. 1919, Lea and Febiger, Phila- 
delphia and New York. 

Craig, C. F.: Jour. Amer. Med. Assoc, 1921, lxxvii, 827. 



PART I 
GENERAL CONSIDERATIONS 



CHAPTER I 
Impoktance 

The importance of carriers is two fold. In the first place, 
chronic carriers constitute more or less permanent reservoirs of 
pathogenic microorganisms. Cases are usually acute and the 
danger of spread of infection is limited to days. The chronic 
carrier, however, is able to infect his environment or contacts for 
months or years. While the acute case excretes more germs and 
probably causes most cases after an epidemic starts, the carrier 
is able to start the epidemic itself by storing the germs until 
seasonal or other conditions are favorable for an outbreak. Some 
workers claim that in this way a carrier will always be found as a 
connecting link in any considerable series of cases. According to 
Vaughan, one of the principal contributions of bacteriology to 
epidemiology is the teaching about carriers. 

Soon after the recognition of the infectious nature of many 
diseases, it was thought that the environment of cases was heavily 
contaminated with germs. In this period efforts were directed 
especially at the disinfection of water, milk, clothing, and fomites. 
It was soon learned, however, that many pathogenic germs live 
outside the hosts only a short time and that, while much can be 
done by sanitation, the contact avenue of infection remains largely 
open. Attention was then focused on the case itself. It was 
taught that if all acute cases were detected early and isolated the 
streams of disease would dry up. But again it was soon found that, 
while much can be done along these lines, there is still a good sized 
flow from the carrier reservoir. At present, therefore, much at- 
tention is being devoted to this other personal source of infection. 

The second reason why carriers are important in preventive 
medicine is, of course, the fact that they are apparently and prac- 
tically healthy. The case, confined to bed or to a sick room, 
limits the spread of parasites, consciously or unconsciously. The 
carrier, however, usually unaware of his condition, moves about 
freely, infecting his environment or contacts without notice. It 

21 



22 CARRIERS IN INFECTIOUS DISEASES 

is this circumstance which has made the subject so dramatic to the 
laity and so serious to the profession. 

The importance of carriers varies in different diseases. In a 
few instances, such as typhoid, enough information is becoming 
available to actually estimate the number of cases due to carriers 
as compared with those due to other cases. In other diseases the 
exact relative importance of carriers is not so well known, but the 
carrier has a definite place in the epidemiology of cholera, dysen- 
tery, diphtheria, cerebrospinal meningitis and malaria. The 
organisms can be identified and traced. In some diseases, such 
as smallpox and measles, carriers are not important, according to 
usual statements. This position is based on epidemiological 
evidence which may or may not have been rightly interpreted. 
Until more is known about the organisms causing many diseases, 
no adequate statements can be made about their carrier aspects. 

There is undoubtedly a tendency at times to overestimate the 
importance of carriers. Other cases, including mild ones, should 
be considered as a cause of a given case before a carrier is sus- 
pected. It should also be remembered that many so-called car- 
riers are really pseudo-carriers who are simply parasitized by non- 
virulent organisms. Those organisms may resemble pathogenes 
morphologically and a presumptive diagnosis may be made. But 
virulence tests nearly always show that some suspected organisms 
have no significance. Hence, while recognizing the real impor- 
tance of the true carrier as a reservoir of pathogenic parasites and 
as an unadvertized danger, the practitioner of preventive medicine 
must recognize the relative importance of carriers in different 
diseases and the existence of the pseudo-carrier. 

On the other hand, there is in some quarters a tendency to 
belittle the carrier program as ineffective. This tendency, I 
believe, is a mistaken one. It is based simply on our insufficient 
knowledge or inadequate control. We should not give up the 
advantage won by the known existence of carriers of pathogenic 
organisms because we cannot always assign them a definite place 
in the unknown whirl of atoms or control their activities. It 
should be realized that only rarely has the carrier plan of attack 
on an infectious disease been given a thorough trial. A certain 
amount of work has been done, but it is usually not complete and 



IMPORTANCE 23 

radical because of the limitation of facilities and control. The 
plan breaks down because the work is too extensive. This 
circumstance has lead some workers to minimize the program. 
It is impossible, however, to sucessfully attack the principles of 
phorology. The only question is how far the details should be 
carried out. As laboratory facilities become more numerous and 
reliable, and as scientific control of events becomes more estab- 
lished, the proper amount of attention will be given to this rational 
plan of attack on our competitors in life. 

The importance of carriers can be realized by considering, first, 
the percentage of cases which become convalescent carriers, then 
the percentage of contacts who become contact carriers and then 
the percentage of both kinds of carriers in the general population. 
Best of all, however, is the actual demonstration of the spread of 
organisms by a carrier in a specific group of cases. 

The study of carriers is valuable to the medical student as it 
shows him something of the biological background of disease 
which has been so useful in orienting the medical sciences. Car- 
riers form a link in the natural history of disease. To understand 
them is to acquire a liberal medical education and to control 
them is to aid in defending and extending civilization. The 
different phases of carrier work involve anatomy, physiology, 
bacteriology, parasitology, pathology, immunology, medicine, sur- 
gery, sanitation, hospitalization, quarantine and follow up service. 

The general practitioner needs to know the best teaching about 
carriers as he is in the most strategic position to break up the 
parasitic balance in favor of man. Too often, either through 
ignorance or limited view of responsibility, this opportunity is 
lost. Patients are carried through a severe infection with skill, 
but are turned loose, without release cultures, to inflict the same 
disease on others. By insisting on release examinations in any 
case whose cause can be found by such examinations, the practi- 
tioner can have the satisfaction of practising preventive medicine 
at the most critical period. If the examination is negative, the 
case can be completely closed and the patient is better satisfied. 
If the examination is positive, the patient may be a temporary 
convalescent carrier and may clear up with a short extension of 
convalescence. If the case becomes a chronic carrier, he can in 



24 CARRIERS IN INFECTIOUS DISEASES 

some instances be cured and at least he can be instructed in 
personal hygiene. If he does not respond to social obligations, 
restrictive measures must be applied. In diphtheria, this ground 
is already covered by regulations, but in several other diseases the 
practitioner decides what shall or shall not be done. It is much 
easier to ignore this subject, but microorganisms can not be 
trusted. There will be no general advance in the prevention of 
many diseases until the general practitioner helps by detecting 
and handling convalescent carriers. 

Most of all the public health official must realize the importance 
of carriers as his position is due to a social demand for supervision 
of the health of groups, among whom carriers are sure to be found. 
He must officially be in position to diagnose and handle carriers. 
Carrier work among private physicians is largely voluntary and 
depends on the degree of social consciousness of the individual. 
The public health official, however, is paid to be socially minded. 

The organization includes, first, the laboratory for the discovery 
of carriers, and second, regulations to secure appropriate action. 
The needs of the laboratory are more fully discussed under the 
heading of diagnosis. It is sufficient to say here that nowhere 
can the laboratory facilities be considered adequate for the work 
that might be done. Of course the question is an economic and 
social one. Do the results justify the expense and trouble? The 
answer here as elsewhere seems to be that, as scientific knowledge 
increases, there is an increasing demand for its application in the 
amelioration of human life. 

On the administrative side, there are many perplexing questions 
of policy in handling carriers. The uncertainty of our knowledge 
in some diseases and the fallability of laboratory workers often 
add to the confusion. But one point should be kept clear. The 
interests of the group of race are supreme over those of the in- 
dividual. This decision has been handed down by Nature and 
by Society and other decisions must conform. The interference 
with the individual should be as slight as possible, but there 
should be no question about the principle that governs. 

Vaughan, V. C: Epidemiology and Public Health. 1922, C. V. Mosby 

& Co., St. Louis. 
Conklin, E. G. : The Direction of Human Evolution. 1921, Charles 

Scribners Sons, New York. 



CHAPTER II 
Pathology 

The pathology of carriers includes specific lesions and a general 
or local immunity. The anatomical basis is an important factor, 
but immune reactions underlie the phenomenon as a whole. 
While there are many unknown elements in the equilibrium be- 
tween host and parasite as seen in carriers, there is also available 
much actual knowledge or suggestive information. 

In the temporary contact carrier there is probably no demonstra- 
ble lesion. The organisms apparently live and multiply for a 
short time on mucous surfaces and then die off or are washed away 
by the secretions. The tissues are immune and in the absence 
of actual proof the most that can be imagined is a slight preexist- 
ing lesion which produces an increased secretion of mucus as a 
temporary focus. 

In the chronic contact carrier, however, some definite preexist- 
ing lesion is often found upon which the parasite becomes in- 
grafted. There is probably a slight re-infection in the immune 
host. As soon as the cause of the primary lesion is removed, as, 
for example, by extraction of a foreign body or the correction of a 
deformity, the carrier state becomes temporary again. The 
carrier lesion, in itself ; is here again very superficial. 

The lesion of the incubationary carrier is of course the slight 
inflammation produced in the tissues by the first invasion of the 
parasite and its early multiplication. Natural lesions of this 
kind are rarely obtained for study, but experimental lesions fill 
in this gap. In the early stages of infection, the microorganisms 
are found on the epithelial surfaces, penetrating between the cells 
(Cecil and Blake). There is some capillary dilatation and oedema 
and a migration of leucocytes. Once past the epithelial barrier 
the organisms spread along the lymphatics, multiply and break 
out again through the epithelial covering into open spaces. The 
course of the lesion is then the usual one for the specific organism. 
From the carrier point of view, the important fact is that, during 

25 



26 CARRIERS IN INFECTIOUS DISEASES 

this early period, there is often the greatest multiplication of the 
parasite and hence the greatest danger of transmission. 

The lesion of the chronic convalescent and relapsing carrier is the 
most definite one. It is also the most persistent, the most dan- 
gerous and requires the most treatment. The lesion is a small 
surviving infection in a generally immune host. It dates back to 
the original attack and has survived the processes which have pro- 
tected the individual as a whole. The organisms are walled off 
or protected from the immune mechanisms and live on indefinitely 
— as balance is reached. The lesion may be slight, even micro- 
scopic, but has been found with great regularity in the best known 
carrier conditions. 

There are two especially important sites of chronic convalescent 
inflammation — the tonsil and the gall bladder. Other similar 
foci occur in other parts of the body, but the lesions of these two 
organs may be taken as types, one of the large field of respiratory 
carriers and the other of the large field of intestinal carriers. 
Chronic tonsillitis and cholecystitis should, therefore, be con- 
sidered in some detail. 

Chronic tonsillitis. This lesion explains the existence of many 
carriers of virulent diphtheria bacilli and hemolytic streptococci. 
It is probably also primarily or secondarily responsible for carriers 
of pneumococci, meningococci, staphylococci, influenza bacilli and 
the organisms of Vincent's angina. Filterable viruses are also 
carried in the tonsils. 

One of the recognized functions of the tonsils, adenoids 
and other lymphatic structures of the upper respiratory and 
alimentary tract is to help protect the body from infection. 
Pathogenic bacteria are picked up by these phagocytic lymphoid 
structures and an attempt is made to destroy them, as in acute 
tonsillitis. This function is undoubtedly a valuable one and ac- 
cording to the general consensus of opinion should be preserved 
early in life. In many cases, however, this function becomes 
perverted. The tonsil is unequal to its task and the microor- 
ganisms, instead of being killed, find a permanent home. The 
policeman, instead of arresting the criminal, is forced to become 
an accomplice. Under these circumstances the tonsil becomes 
an individual and social liability rather than an asset. It is 



PATHOLOGY 



27 



often best to lose the perverted protective function by removal 
of the organ or by X-ray treatment. 

The average tonsil is not normal in the sense of healthy lym- 
phoid tissue covered with intact epithelium. Almost every 



% t f -^S5j v > 












Fig. 1. Section of Tonsil of Chronic Diphtheria Carrier. X 50 
Shows loss of epithelium and fibrinous exudate in tissue 

tonsil which is examined shows some disintegration of epithelial 
covering with exudation and signs of inflammation, due to infec- 
tion with various pathogenic parasites (fig. 1). In addition to 
these and as illustrating the favorable conditions for parasitism, 



28 CARRIERS IN INFECTIOUS DISEASES 

various other harmless parasites are found, such as amoebae and 
leptothrices. An undescribed yeast-like organisms with no in- 
flammatory reaction about it is present frequently in sections 
(fig. 2). 







• 


* 


1 . 

m 

s 

% * 


* 


"* '. 


* 1 





Fig. 2. Unidentified Yeast-Like Organisms Frequently Found in Sections of. 

Tonsils. X 400 
MacCalhim stain. Note absence of reaction around parasites 

The tonsil, therefore, is often a hot bed for microorganisms. 
The crypts become incubators instead of disinfcctors. Heat, 
moisture and food are supplied by the body while the antiseptic 
action of the tissues and body fluids is neutralized by poor drain- 
age. The structure of the crypts with their blind cuds, tortuous 



PATHOLOGY 29 

channels and ''underground" connections make an ideal nest or 
home for these parasites (fig. 3). With such an organ as this at 
the gateway to the body, it is easily realized that the chances for 
carrier production are particularly good. Temporary and chronic 
convalescent carriers are especially apt to develop. 

The same situation exists with less frequency in lesions of the 
sinuses, turbinates, septum, gums and other structures of the nose 
and mouth. 





Fig. 3. Photograph of Tonsil Injected with Lampblack and Paraffin 

to Show Crypts 
"Underground" connections are emphasized. Preparation by Sturm 

Chronic cholecystitis. The gall bladder has of course an entirely 
different function from the tonsil, but, in its carrier relationship, the 
entire gall bladder may be compared to a crypt of the tonsil. The 
wall is slightly invaded in a chronic process and the contents consist 
of a rich culture of typhoid or cholera bacilli. Apparently the 
bile neutralizes the antiseptic effect of the leucocytes, mucus and 
serum, while the addition of these substances increases the nutri- 



30 CARRIERS IN INFECTIOUS DISEASES 

tious value of the bile. The result is a very effective multiplying 
and distributing agency. 

Much work and speculation have been devoted to the subject 
of the mechanism of gall bladder infection. The possibilities of 
infection are (1) ascending, through the common and cystic ducts 
from the intestine, (2) embolic, in the blood and lymph vessels of 
the bladder wall, (3) descending, through the bile from the liver. 
Any of these methods may occasionally occur, but ascending in- 
fection is apparently rare. Evidence from some experimental 
work in rabbits seems to favor an early small embolic lesion of 
the wall with subsequent general infection of the contents and 
wall (Meyer). Other experimental work favors the descending 
route, as large numbers of bacteria are excreted from the blood by 
this method and an inspissation of bile is known to occur in the 
bladder. This theory also draws some support from the fact that 
a large number of carriers occur among women in whom biliary 
stasis is more frequent. The important fact is that, whatever the 
earliest lesion, the end result is a general mild catarrhal inflam- 
mation of the wall with infection of the contents of the cavity. 

The cholecystitis starts as an acute mild process during the 
original disease and persists indefinitely. When examined after 
operation or autopsy, these gall bladders have a thickened wall 
and altered contents. The ordinary uniform brown bile is re- 
placed by a yellowish or whitish fluid with sediment of purulent 
flakes. One or more gall stones are present. 

The wall shows a general catarrhal inflammation. Ulceration 
does not occur except possibly early and no lesions of the wall are 
found except in the submucosa. Here there is a uniform collection 
of lymphocytes indicating a reaction to infected contents (fig. 4). 
The epithelial wall may show nests of bacilli (fig. 5). 

The carrier state can be produced experimentally in a certain 
percentage of rabbits by intravenous injection. The gall bladder 
lesions are of value in attempts at chemotherapy and for demon- 
stration. Gay and Claypole state that by a special technique 
they are able to make 100 per cent of carriers. Ordinarily, about 
30 per cent of carriers result from the injection of sub lethal doses. 
Freshly isolated cultures arc most effective. 



PATHOLOGY 31 

In some carriers the surviving lesion seems to be confined to the 
gall bladder as excision of this organ results in bacteriological cure. 
In others, however, there must be other lesions in other parts of 
the biliary system, probably higher up in the smaller bile capil- 










Fig. 4. Section of Gall Bladder in Human Typhoid Carrier. X 70 
The section shows that the lesion is confined to the mucous membrane 
of the bladder. There is a mild general catarrhal inflammation with 
migration of leukocytes into the submucosa. 

laries, because cholecystectomy, in some carriers, does not result 
in cure. No practical way of determining the existence of exact 
location of this lesion is available at present. These lesions of the 
liver in carriers are not well understood but they may originate 
in the so-called focal necroses which are really emboli of endothe- 



32 



CARRIERS IN INFECTIOUS DISEASES 



lial cells. In experimental work, infection of the smaller bile 
capillaries occurs with the production of multiple cysts resembling 
a bunch of grapes. 




Fig. 5. Drawing of Section of Gall Bladder in Experimental Typhoid 
Carrier State in Rabbit. X 800 
Nest of typhoid bacilli is seen in epithelial coat and the collection of 
leukocytes is seen in the submucous coat. 



PATHOLOGY 33 

The other lesions of intestinal carriers are chronic ulcers of the 
intestines which will be discussed under dysentery. 

The lesions of the urinary carrier are much the same as those of 
the intestinal carrier. The lesion is really in the hilum of the 
kidney — a chronic pyelitis with secondary cystitis. The lesion 
is a surviving one and the same questions of pathogenesis arise 
as in case of the cholecystitis. 

In addition to the actual lesion, the general state of immunity 
of the body is of great importance in carriers. In incubationary 
carriers there is naturally no immunity or only a beginning one. 
In convalescent carriers there is a general immunity, but not a 
local one. In some instances the carrier state probably keeps up an 
immunity by continuous vaccination. The organisms in the 
focus stimulate the formation of immune bodies such as agglu- 
tinins, opsonins, bacteriolysins and complement fixing bodies. 
These are not present regularly or in strong concentration and 
suggest a balanced immunity. In relapsing carriers the balance 
is delicate and easily upset, especially in protozoal infections. In 
true contact carriers there is a general or local immunity. No 
evidence is found of active immune processes. 

Cecil, A. L., and Blake, F. G.: Jour. Exp. Med., 1920. 

Barnes, H. A.: The Tonsils, Faucial, Lingual and Pharyngeal. 1914, 

C. V. Mosby Company, St. Louis. 
Meyer, K. F.: Jour. Inf. Dis., 1921, xxviii, 381. 
Nichols, H. J.: Jour. Exp. Med., 1916, xxiv, 497. 
Rous, Peyton and McMaster, P. D. : Jour. Exp. Med., 1921, xxxiv, 47. 
Bloomfield, A. L. : Bulletin of the Johns Hopkins Hospital, 1921, xxxii. 



CHAPTER III 
Diagnosis 

The adequate diagnosis of a carrier involves (1) the identifica- 
tion of the specific parasite, or of specific immune substances; 
(2) the location and significance of the focus in the host; (3) the 
relation of the carrier to his environment and contacts. The 
diagnosis is, therefore, a combined one depending on laboratory, 
clinical and epidemiological work and should be accomplished by 
"cooperation" rather than by "competition" between the pathol- 
ogist, the physician and the sanitarian. Of course, some one 
gifted and energetic individual may in turn find the germ, examine 
the patient and follow the trail in the group. This has been the 
most common method in the development of the carrier work and 
undoubtedly it is best for some one person to gather up all the 
threads of the story. As the whole carrier movement started in 
the laboratory, the laboratory specialist often takes the lead, or 
is expected to do so. But the work has now reached the stage 
where more organization is needed. No one person can do justice 
to all aspects of the situation. The requisite for effective work is 
the intelligent cooperation of all concerned. 

In the laboratory diagnosis, the finding of the specific organism 
is usually the aim. Details of suitable methods are given later 
under each infection. In general it may be said that specific 
diagnosis is more difficult in carriers than in cases. There are 
usually more individuals to be examined. The organisms are 
usually less numerous and may be more mixed with other organ- 
isms. In addition, there is more doubt about virulence and, if 
virulence tests are available, these must be made. There are also 
increasing complexities of groups and subgroups which must be 
considered. 

In some diseases a tentative diagnosis can be made on the pres- 
ence of antibodies, which are as specific as the parasite itself. 
Of the antibodies, the agglutinins are the easiest to detect and 
have been most used. As far as is known, they are as reliable as 

34 



DIAGNOSIS 35 

any others in carrier work. Agglutination is an especially valuable 
measure in dealing with veterinary carriers. Allergic skin tests 
have been proposed as an aid in detecting carriers. If reliable, 
such tests would be of great value. As yet, however, they are not 
on a practical basis in human medicine. Naturally all these 
immune reactions are indications only of infection. They do not 
distinguish between a case and a carrier, but they may aid in the 
final diagnosis. 

In addition to attempting to find the parasite or evidences of 
its presence, the laboratory may be called on to determine the 
susceptibility of possible hosts or at least to supply the biological 
materials, if such tests are practicable. 

It is evident that, with this primary dependence on laboratory 
methods, the work of the laboratory must be reliable. The 
clinical check is slight at best. Hence, the personnel and equip- 
ment of a phorological laboratory must be even better than those 
of a laboratory of clinical pathology. The pure technician is, 
therefore, of limited value in carrier work. The type needed is the 
specialist who has emerged from a general medical background. 
As has already been said, laboratory facilities have practically 
never been sufficient for the work which might be done. If 
carrier work is worth while, as it seems to be, more support, 
financial and moral, should be given to the laboratory. 

The clinician can aid in the finding of the parasite by picking out 
suspects for examination. Meningococcus carriers are more apt 
to be found among persons with large amounts of mucus in the 
nasopharynx and streptococcus carriers among those with large 
tonsils. Typhoid carriers sometimes have local signs or symptoms 
of cholecystitis. The personal history of disease is also often 
suggestive. Another useful field of clinical activity exists in the 
actual securing of a satisfactory specimen for laboratory examina- 
tion. Much lost motion and confusion results from the examina- 
tion of poor specimens. To obtain a good specimen from the 
tonsils, nasopharynx, sinuses, duodenum, or ureters requires con- 
siderable technique which should be furnished by the clinician or 
by his organization of technical assistants and nurses. 

After the presence of a virulent organism in the body has been 
established, a clinical survey is necessary to locate the focus, to 



36 CAKRIERS IN INFECTIOUS DISEASES 

decide the diagnosis between a carrier and a mild case or to 
classify the carrier. This work can be properly done only by a 
clinician. Altogether, therefore, the physician has an important 
part to play in the diagnosis. 

Like the clinician, the epidemiologist can assist in the diagnosis 
by picking out the most suspicious individual or group for ex- 
amination. Of course the possible contacts and sources of in- 
fection are often innumerable and the most effective method 
would be a complete examination of all persons. There would 
then be available a complete record of their parasitological status. 
But such a state of affairs is for Utopia, not for our work-a-day 
world. The medical Sherlock Holmes can often get a clue from 
the general situation which can be followed up in the laboratory. 
The number to be examined can often be narrowed so that a few 
persons can receive especial attention. This result requires, of 
course, the usual epidemiological investigations of personal habits, 
occupation, journeys, and so forth. 

When the carrier is once diagnosed, individually, the epidemi- 
ologist must be depended on to make the social diagnosis. The 
rinding may mean much or little according to circumstances. 
Hence, in the last analysis, the epidemiologist should be the 
coordinator in carrier work. 






CHAPTER IV 

Treatment 

The treatment of carriers has one unusual factor. Unlike the 
case, the carrier must be convinced that he needs medical atten- 
tion. The correction of the trouble also has more social than 
individual value. Hence, self-interest is often directly against 
any treatment. The situation should be handled along the fol- 
lowing lines. Carriers usually have chronic infections. These 
may become acute at times and make more trouble. Moreover, 
all current medical teaching favors the removal of chronic foci 
of infection for the good of the individual. Hence, a carrier has 
personal reasons for being treated. In addition, the interests of 
society are paramount to those of the individual. The individual 
should recognize his social obligations and as far as possible not 
do harm to others. If he is unwilling to accept this point of view 
he may be forced to it. As was shown in the great war, society 
will not tolerate individual action which is anti-social in emer- 
gencies, and cases of infectious disease are more and more being 
regarded as emergencies. Reason is effective with many carriers 
discipline with others, but some can be handled only by force. 

The treatment of carriers includes technical methods, instruc- 
tion in personal hygiene and administrative or legal measures. 

The technical treatment of infections as applied to carriers 
consists of the following procedures: 

a. Good hygiene, local and general, to assist in the natural 
processes of combatting microorganisms. These measures are 
especially valuable in handling temporary contact carriers, such 
as meningococcus carriers. 

b. Specific anti-microbic treatment, which consists of the use 
of vaccines and sera. These measures in general have been dis- 
appointing, but analogy and partial success keep alive the possi- 
bility that these measures may some time be effective. As the 
focus in convalescent carriers has persisted in spite of a general 
immunity which has practically cured the patient, little effect 

37 



38 CARRIERS IN INFECTIOUS DISEASES 

might be anticipated from specific vaccines or sera. In fact, 
experience has shown that typhoid vaccination does not cure 
typhoid carriers with any regularity and diphtheria antitoxin and 
vaccine do not cure diphtheria carriers. The whole subject of 
the therapeutic use of vaccines is in such a state of uncertainity 
that definite statements cannot be made. 

The use of non-specific vaccines has also been tried with the 
idea of producing a reaction which might clean up a carrier 
lesion in the same way that it sometimes affects other chronic foci. 
This measure may have turned the balance in some carriers, but 
many are resistant. 

c. The local use of disinfectants. This is a logical procedure 
but is not completely successful in practise. The number of 
organisms may be reduced and, with this reduction, the danger of 
transmission may be lessened, but cure is not regularly attained. 
During the war, elaborate devises, such as gassing chambers, were 
used for the large number of carriers. The consensus of opinion 
is that specific action was not proved. In some instances, the 
antiseptics seemed to injure the natural resistance of the mucous 
membrane and the organisms grew out in pure culture. 

d. Specific chemotherapy. The carrier has been a particularly 
attractive subject for workers in chemotherapy and a great many 
compounds have been tried experimentally, especially in gall 
bladder infections. At present it cannot be said that any one 
compound has won its way clinically except the arsphenamine 
series in spirochete carriers. Mercury, quinine, emetine and 
antimony of course have their place in the treatment of carrier 
infection. 

e. The most successful local method of treating carriers is the 
removal of the focus by surgical operation. This measure has 
been successful in over 50 per cent of typhoid carriers and in over 
80 per cent of diphtheria carriers. Under this head come also 
corrective measures, such as the removal of foreign bodies and the 
opening of obstructed air passages. X-ray and radium have been 
tried as a substitute for surgery. They have failed to influence 
gall bladder lesions, but in some instances contract the tonsil 
and may be a method of choice under certain circumstances. 
Unfortunately the lesion may be reduced but the organisms may 



TEEATMENT 39 

persist. Repeated treatments may be necessary and, for prompt 
and permanent results, tonsillectomy is preferable. 

The results of surgical treatment of carriers confirm the conclu- 
sion drawn from experimental and pathological study of the sub- 
ject, namely, that the chronic carrier state is really an infection 
which is usually sharply localized. 

The surgical treatment of carriers calls for cooperation on part 
of the surgeon. The diagnosis is usually made by physicians and 
the surgeon is asked to give technical assistance only. At the 
same time, he should accept the program. Some surgeons decline 
to operate except on cases, but this is a limited view of the possi- 
bilities and responsibilities of surgery. 

Aside from purely technical treatment there is with carriers an 
especial reason for "treating the patient as well as the disease." 
The carrier is subject to isolation and ostracism. During the war, 
in one battalion, the men threatened to kill a meningococcus 
carrier who had, of course unconsciously, infected and caused 
the death of several companions. Some individuals cannot 
understand the situation and become depressed and psychoneu- 
rotic under quarantine and continued examination. The circum- 
stances should be clearly and simply explained and an effort should 
be made to stimulate the individual's social morale. His incon- 
venience is for the good of the greatest number. In suitable 
cases a radical cure should be attempted. Otherwise a carrier 
should be instructed in personal hygiene and be examined at inter- 
vals and inspected for observance of rules. In dealing with irre- 
sponsible persons, forcible detention may be necessary as a last 
resort. 

In the handling of carriers, personal hygiene must be given a 
prominent place, as intelligent cooperation will accomplish results 
when treatment fails or when quarantine is impossible. The 
object of personal hygiene in this case is the social one of protecting 
others, but when properly approached, few individuals will fail 
to respond to some social obligation. 

If carriers are quarantined in hospitals, the number may be so 
large that a special ward for isolation and observation may be 
necessary. In this case the social service and vocational workers 
should assist in keeping up morale. The "working" quarantine 
principle should also be applied. 



40 CARRIEKS IN INFECTIOUS DISEASES 

Prevention. The prevention of the development of carriers is a 
part of preventive medicine, as well as their detection and cure. 
Specific measures for this end are limited at present, as too little 
is known about the mechanism of the production of carriers and 
too few means of influencing that mechanism are at hand. Al- 
ready, however, we know that deformities of the nasal passages 
and the tonsils predispose to carrier conditions. Hence, there is 
an additional argument for good hygiene of the nose and throat. 
It is possible that in typhoid fever, the antiseptic action of the 
bile may be increased by diet or by antiseptics. It is also possible 
that the more severe the disease, the more likelihood there is that 
a carrier state will result. In this case there would be an extra 
argument for good nursing. 

Of course, carriers can be prevented indirectly by preventing 
cases. Carriers can also be prevented in a sense by curing them. 
But the actual prevention of carriers by a complete cure of the 
infection should be a recognized object of the treatment of a case. 
The discharge of a patient without release cultures and appro- 
priate action is as unprofessional as the treatment of a case without 
a knowledge of the diagnosis. 

Altogether the handling and treatment of carriers calls for the 
"do the best you can" philosophy. The subject is so full of 
difficulties that the clean cut, radical and dramatic program, of 
which we are all so fond, cannot often be realized. On the other 
hand, the actual program is not an apologetic one, but has deep 
roots in evolutionary history and practical experience. 

The present day efforts at improved organization and standardi- 
zation should include carrier work. The kind, number and in- 
tervals of diagnostic and release cultures should be more uniform. 
Periods of isolation and quarantine should also be revised in the 
light of increasing knowledge. Most of all, more standard and 
general rules for the handling and disposition of carriers are 
needed. At present each state or smaller unit has its own rules 
or no rules, while what are needed are interstate or national 
standards. National medical societies, especially those devoted 
to public health, have a responsibility for initiating such standards. 

Peterson, Wm. F. : Protein Therapy and Non-specific Resistance. 1922, 

The Macmillan Co., New York. 
Murphy, J. B., et al: Jour. Exp. Med., 1921, xxxiii, 815. 
Murphy, J. B., et al: Jour. Amer. Med. Assoc, 1921, 76, 228. 



PART II 
SPECIAL DISEASES 



SPECIAL DISEASES 

In considering the phorology of each of the most important in- 
fectious diseases it is useful to classify these diseases according to 
their relation to the basic biological necessities of life. These 
necessities are of course self-preservation and self-prepetuation. 
Self-preservation, or continued metabolism, calls for the intake of 
food and drink and the excretion of waste products, for the intake 
of oxygen and the outgo of C0 2 , for the circulation of these and 
other substances and for the control and correlation of the vital 
reactions. Self-perpetuation of course depends on sexual inter- 
course. It also necessitates the recognition of the family as the 
primary social unit. 

In the course of evolution, parasites have become engrafted on 
these functions and the carrier aspects naturally form only a part 
of the infection as a whole. The classification roughly covers the 
avenue both for the intake and outgo of the parasite. Thus we 
have alimentary, respiratory, circulatory and sexual diseases. 
Among the diseases of the nervous system or correlating mecha- 
nism there are no clear cut carrier problems per se as there is no 
natural outlet. The "master tissues" are also well protected 
from direct efforts of the environment such as insect bites. The 
advantages of this grouping are that similar specimens are neces- 
sary for the diagnosis of carriers and that similar means for the 
prevention of carrier action are used in each group. Comparison 
or contrast helps to emphasize the important points. 

It should be understood, however, that this classification is 
primarily a practical and not an academic one. The diseases 
are not strictly limited to any one anatomical or physiological 
system. Moreover, the natural parasitic order is not observed 
as one and the same group may contain diseases due to either 
bacteria, protozoa and to helminths. In short, the object is 
practical and medical rather than purely scientific. 

A. The Alimentary Group, Chapters V, VI, VII and VIII, 
includes those diseases whose parasites enter the body chiefly in 

43 



44 CARRIERS IN INFECTIOUS DISEASES 

food and drink and escape in the intestinal contents — the typhoid 
fevers, cholera, the dysenteries and helminthoses. 

B. The Respiratory Group, Chapters IX, X, XI, XII, and XIII, 
includes the large number of diseases whose specific parasites enter 
and escape from the body chiefly through the nose and mouth. 
The most important members of this group are diphtheria, men- 
ingitis, pneumonia, influenza, colds, all the acute exanthemata, 
poliomyelitis, tonsillitis, and other streptococcus infections, 
Vincent's angina, sinusitis, bronchitis and the other "common 
respiratory'' infections. 

C. The Blood Group, Chapter XIV, might also be called the 
insect transmission group, as the parasites live chiefly within the 
blood vessels and entrance and egress are possible only by puncture 
of the vessel wall. It is desirable, however, not to confuse insect 
carriers with human carriers. The most important diseases from 
the carrier point of view are malaria and filariasis. 

D. The Sexual or Venereal Group, Chapter XV, includes the 
diseases whose parasites enter and the leave the body chiefly by 
sexual intercourse. 



CHAPTER V 
The Typhoid Feveks 

The typhoid fevers include the classical type, the more recently 
differentiated types of paratyphoid A and B, and the latest, C. 
The carrier relationships are apparently the same in all, with the 
exception of some forms of infection with Para B bacilli which 
more nearly resemble bacillary dysentery. 

The importance of carriers in this group is well established. 
Our knowledge of carriers was worked out largely in typhoid and 
there are on record many dramatic and clean cut instances of the 
role of carriers. The number of cases due to carriers has been 
estimated by different observers as from 9 to 50 per cent. This 
percentage is believed to be on the increase, as sanitation and 
hygiene are reducing infection from cases, but are not so effective 
against contact infection by carriers. 

Carriers are especially apt to contaminate food because 80 per 
cent of carriers are women. According to Sacquepee, women 
make up only one-fifth of cases, but three-fourths of intestinal 
carriers. Carriers among children are said to be rare. Close 
contact such as occurs among crews on shipboard has been 
especially favorable for demonstrating the dissemination of bacilli 
from a carrier. Urinary carriers are about one-tenth as frequent 
as intestinal carriers and apparently occur more frequently in 
males. Genuine instances of combined urinary and intestinal 
carriers are very rare. 

Carriers in the general population include of course incubation- 
ary, convalescent and contact carriers. The relative and total 
number of these carriers will depend on the previous amount of 
typhoid; the age and sex group, etc. In general the number is 
much less than 1 per cent, and is unquestionably diminishing on 
account of the reduction of cases. During the war, the examina- 
tion of about 30,000 food handlers in the Army showed less than 
0.1 per cent of carriers among young healthy males. 



45 



46 



CARRIERS IN INFECTIOUS DISEASES 



No satisfactory statistics exist on the relative proportion of 
different kinds of carriers. "Incubationary" carriers and ' 'con- 
tact" carriers have been found in epidemics, but careful clinical 
surveys, including the examination of the duodenal contents, are 
usually lacking. The most instructive results have come from a 
study of convalescent carriers. It has been estimated by Gay that 



■"iiiilliiiiiiliii-i-iliiiiiiiiiliiiiii 
•■■■■■•■■■■■■•■■!■!■■■■■•■•■■■■::■"■•■:■! 



::::::::::::::::::::::::::::::::: 




Chart A. Distribution of Typhoid Bacilli in Cases and in Convalescent 

Carriers 



Percentage of bacilli found in blood + + + + + 

Percentage of bacilli found in urine 

Percentage of bacilli found in feces 

Percentage of bacilli found in duodenal contents 

Percentage of agglutination reactions o-o-o-o 



THE TYPHOID FEVERS 47 

7500 convalescent intestinal carriers are being yearly added to the 
population in the United States. 

In order to illustrate the percentage of different kinds of conva- 
lescent carriers, charts AandB have been prepared which show the 
distribution of typhoid bacilli in the body in cases an din temporary 



Chart B. Distribution of Typhoid Bacilli in Cases and in 
Convalescent Carriers 
Percentage of bacilli found in blood ++ + + + 

Percentage of bacilli found in urine 

Percentage of bacilli found in feces 

Percentage of bacilli found in duodenal contents 

Percentage of agglutination reactions o-o-o-o 



48 CARRIERS IN INFECTIOUS DISEASES 

and chronic convalescent carriers. The agglutination curve is also 
given. The data has been largely taken from Hiss, Zinsser and 
Russell's Bacteriology, from Gay's monograph and from Garbat's 
recent work on duodenal cultures. There are several gaps which 
have been filled in tentatively from the author's experience. 

As will be seen, the charts can roughly be divided into four parts. 
(1) The first month shows the active case, (2) the second month 
shows clinical convalescence with the occurrence of temporary 
carriers, (3) the next four months shows the spontaneous cure of 
many temporary carriers, (4) the next six months shows the per- 
sistence of chronic carriers and the fall of the agglutinative curve 
to a permanent level. 

Cultures of duodenal contents during the disease have not been 
made in any considerable number, but the percentage of cases 
with bacilli in the duodenum must be very high. During con- 
valescence, according to Garbat, 50 per cent more carriers are 
detected by this method than by ordinary examination of the 
feces. 

The curves may drop slightly after six months, but most of 
these chronic carriers persist as far as is known indefinitely. 
Carriers of at least thirty years duration are recorded. 

PATHOLOGY 

In incubationary and pure contact carriers there is no definite 
carrier lesion. The bacilli live and multiply in the intestinal 
contents for a short time, and then in the incubationary carrier 
invade the intestinal wall and in pure contact carriers pass out of 
the system entirely. Various ingenious theories have been de- 
vised to explain permanent contact carriers, but a fair considera- 
tion of the lesions will lead to the conclusion already expressed 
that such so-called contact carriers are really convalescent carriers 
after mild infections. It is an instructive fact that pure contact 
carriers do not give an agglutination reaction. 

In chronic convalescent carriers permanent lesions occur in the 
ducts of two chief excretory organs, the liver and kidney. Chronic 
inflammations due to typhoid bacilli exist in other parts of the 
body, such as the bones, but strictly speaking these are not carrier 
lesions because there is no natural outlet. It might be thought 



THE TYPHOID FEVERS 49 

that Peyer's patches would be a favourable site for chronic ulcera- 
tion, but this is not the case. Purely intestinal lesions rarely make 
a basis for carriers, and pathologically the term "intestinal" carrier 
should not be used unless such a lesion is demonstrated. The 
great majority of intestinal carriers are gall bladder or bile duct 
carriers. Similarly, from the pathological point of view, a pure 
urinary carrier probably does not occur. There is a definite lesion 
usually in the pelvis of the kidney with secondary pyelitis and cys- 
titis. Other chronic foci in the genito-urinary apparatus have 
been considered possible but have not been demonstrated. 

As was said in Chapter II, the pathogenesis of these lesions, 
especially that of the gall bladder, has been occasion of much 
speculation, many experiments and various conclusions. The 
exact steps of the process are not yet fully agreed upon, but the 
end result is well recognized. The explanation is not entirely an 
academic question, because the success of therapeutic attack may 
depend on mechanism of the lesion, whether produced through 
the bile or through the blood. In any case, there is an unfortu- 
nate neutralization of the natural defenses of the body. The bile 
destroys the complement and helps neutralize other antibodies 
while the serum and mucus neutralize any antiseptic action of 
the bile. 

These carrier lesions date back to the original attack as mild 
complications which are usually unnoticed. At autopsy on cases 
dying of toxaemia, some cases of mild cholecystitis are found with 
definitely inflamed walls. Typhoid bacilli are present in the 
bile in all cases, but these early cases with lesions are the ones 
which later develop into carriers. 

Carrier strains of the organism do not differ in any known way 
from strains from cases. There is no simple test for virulence or 
pathogenicity, but typical human infections have occurred from 
accidental contamination of the mouth with carrier strains. 

DIAGNOSIS 

The final diagnosis must necessarily be made by laboratory 
methods, but the personal history, a clinical examination, or 
epidemiological evidence may suggest a tentative diagnosis. 
Many carriers give a good history of the original attack or of some 



50 CARRIERS IN INFECTIOUS DISEASES 

suspicious illness. Some complain of occasional soreness or ten- 
derness over the gall bladder and give general evidence of being 
below par. One or more individuals may be put under suspicion 
by the circumstances of the epidemic. 

The laboratory diagnosis is a bacteriological one, but a sero- 
logical examination may be suggestive. Over 50 per cent of car- 
riers give the agglutination test or Widal reaction as an indication 
of their chronic forcus. The serum titre is usually about 1:40. 
This test, however, has little value in early convalescents and in 
those who have recently been vaccinated against the disease. 

The bacteriological diagnosis consists in isolating and identify- 
ing the typhoid organism concerned. Usually the feces and urine 
are examined^. A single examination of stool is not conclusive; 
even in the urine the findings may be irregular. A single examina- 
tion of duodenal contents is much more conclusive. The bacilli, 
if present, are in more nearly pure culture than after being mixed 
in the contents of thirty feet of intestine. Conclusive results can 
be obtained, according to Garbat, by examining two consecutive 
specimens of duodenal contents, two consecutive specimens of feces 
and two consecutive specimens of twenty-four hour urine. 

On the occurrence of a case or cases which cannot be explained 
by other methods of infection, a search for carriers is indicated. 
The circumstances are investigated and, allowing for the incuba- 
tion period, certain suspects are picked out. The feces and urine 
of the suspected contacts are examined once. This examination 
may detect a carrier who can then be further investigated. If 
this examination is negative, a Widal reaction should be made, 
if possible, and anyone with a positive reaction should be re- 
examined by the duodenal tube method. Any suspects with a 
positive or doubtful history should also have a reexamination of 
duodenal contents. Some one of these examinations will usually 
give positive results. 

In routine surveys, the feces and urine of all individuals should 
be examined once. History of the disease should be inquired into 
and those with a positive or doubtful history should be reexamined 
by the duodenal tube method. 



THE TYPHOID FEVERS 51 

SPECIMENS 

Feces. Loose stools are more favorable for positive results as 
the bacilli are brought down from the duodenum more rapidly. 
Calomel has the reputation of being a good cathartic for carrier 
specimens. Dried bile is also used. Individual specimens are 
easily obtained by providing the patient with a labelled container 
and directing them to use a chamber. A convenient form of 
container is a glass vial with a metal scoop fastened to the cork. 
A pill box of tin or card board with a tongue depressor for collec- 
tion may also be used. All containers should have a blank paper- 
label for identification of the specimen. If the specimen cannot 
be examined within a few hours, the vial should contain a mixture 
of 30 per cent glycerin in salt solution which keeps the typhoid 
group of organisms alive for a longer time. One part of feces 
should be mixed with about two parts of solution. 

For collecting large numbers of specimens more organization is 
necessary. The most certain method is to take the specimen 
direct from the rectum. A cotton swab is put into a piece of 
glass tubing about 10 mm. in diameter, the end of the tube is 
vaselined and gently forced through the anus. The swab is then 
pushed into the rectum, rotated and withdrawn and put in a 
sterile tube or in the glycerine solution mentioned above. The 
swab alone can be used, if the cotton is firmly attached and the 
buttocks are well separated. Care must be used not to break off 
the end of the swab in the rectum. An enema tube can also be 
used to advantage as fecal contents collect in the opening. Other- 
wise wooden or paper plates or pieces of wood can be used to re- 
ceive the movement and, after the specimen is taken, these can 
be buried or burned. 

Urine. Urine should be collected in a small sterile bottle. A 
catheterized specimen is not necessary for diagnosis. Some ob- 
servers recommend a specimen from a mixed twenty-four hour 
collection. Positive urine is often cloudy and very rich in bacilli. 

Duodenal contents. This specimen can be obtained with less 
difficulty than might be expected. An Einhorn tube, or modifi- 
cation, is used (fig. 6). The procedure should be carried out on a 
nearly empty stomach and duodenum. The early morning is 



52 



CAKRIERS IN INFECTIOUS DISEASES 



a favourable time, after a light breakfast. The patient sits up 
on a bed or couch. The metallic tip is chilled and then swallowed 
while the operator gives moral support. The patient should then 
lie down on right side with knees drawn up and rest as the tube 
gradually descends. Usually one to two hours are required. 
Some workers give the tube in the evening and make the examina- 




Fig. 6. Picture of Duodenal Tube 
A convenient variety of the Einhorn Duodenal Tube, some form of 
which is essential in efficient typhoid carrier work. 

tion in the morning. This long procedure has never been neces- 
sary in my hands. A flow of fluid should be established by syphon- 
age or by slight suction with a syringe. The first fluid is, of 
course, stomach contents. A test of reaction should be made with 
litmus or better with methyl red and phenol red (0.02 per cent 



THE TYPHOID FEVERS 53 

watery solution) . The former is red in an acid medium and yellow 
in an alkaline one. With phenol red the colors are reversed. As 
soon as a change occurs in the color or consistence of the flow, a 
fresh container should be used to receive the material and another 
test of reaction should be made. Usually when the duodenum 
has been reached a yellow syrupy fluid appears which reacts yellow 
with methyl red and red with phenol red. This specimen is then 
examined in the laboratory. Naturally, if acid gastric juice is 
submitted for examination, no information of value will be ob- 
tained. While the tube is still in place, the Lyon technique can 
be carried out, which consists in pouring into the tube, through a 
small funnel, about 30 cc. of a 25 per cent solution of magnesium 
sulphate. Syphonage is then reestablished and frequently a 
darker colored fluid or "B" bile is obtained. If this is really gall 
bladder bile, it would be preferable to plain duodenal contents, 
but as duodenal contents are usually satisfactory and there is 
doubt about the origin of B bile, this procedure for carrier work is 
an unnecessary refinement. 

TECHNIQUE 

The duodenal contents are spread directly on Endo plates. 
Some of the specimen should also be incubated for twenty-four 
hours and other plates inoculated. A microscopic examination of 
the centrifuged sediment may show leucocytes in positive cases. 
The further procedure is given below. 

A drop of liquid feces or a mixture of hard feces in broth is 
spread on the surface of differential media and search made for 
colonies characteristic of the typhoid group. Only by experience 
can the proper amount of inoculum be judged. It is best to use 
several plates and the usual trouble is too many rather than too* 
few colonies. Some workers enrich specimens with dilutions of 
brilliant green. This method succeeds at times, but fails at others. 
If the time which the bacteriologist might devote to enrichment 
were spent in securing specimens of duodenal contents, the end 
results would be much better. Many differential media have been 
proposed, such as lactose litmus agar, eosin methylene blue agar, 
malachite green, phenol red or brom cresol purple media. All 
have their merits and drawbacks. In the Army Medical School 



54 CARRIERS IN INFECTIOUS DISEASES 

method, worked out by Russell, Endo medium is used and in spite 
of some drawbacks, is most serviceable. As it rapidly deteriorates, 
the ingredients are kept separately — 3 per cent extract agar, pH 
7.8, is kept in flasks and sterile solutions are prepared of 10 per cent 
lactose, saturated alcoholic solution of basic fuchsin and 10 per 
cent watery sodium sulphite. A few hours before use, the agar 
is melted, and the ingredients are added — 1 per cent lactose, 1.8 cc. 
fuchsin and about 25 cc. sulphite to the liter. The agar should 
then be cooled to about 50° and poured into Petri dishes, small or 
large. The agar is allowed to harden with the cover ajar in a 
dust free place. The specimen is then spread with a loop or a 
right angle glass spreader. Incubate twenty-four hours and ex- 
amine for colorless, translucent, non-lactose fermenting colonies. 
Mark and transfer several to Russell double sugar tubes, inoculat- 
ing both butt and slant (3 per cent agar with 1 per cent lactose, 
0.1 per cent glucose, pH 7.6 and phenol red as an indicator). If 
the colonies are numerous enough, agglutination can be done 
immediately with colonies made up of small Gram negative 
bacilli. 

The double sugar tubes are incubated for twenty-four hours and 
are then examined for characteristic appearance of the typhoid 
group. This for the typhoid bacillus is an acid butt with no gas 
bubbles and an alkaline slant. With Para A or B, the butt is 
acid and broken up with gas bubbles ai\d the slant is alkaline, 
especially so with Para B. Colon bacilli produce more gas in the 
butt and an acid slant, which, however, may turn alkaline in case 
of B. aerogenes. 

Growth from typical double sugar tubes are stained and if 
Gram negative bacilli are found, agglutination is done with spe- 
cific sera by transferring a suspension or a loopful to different dilu- 
tions of serum. If satisfactory agglutination and controls result, 
the diagnosis is made. The culture should be plated out and a 
pure culture kept for reference or confirmation. 

The urine is plated direct in liberal quantity and also incubated 
in about five parts of broth and plated again after twenty-four 
hours. The growth of bacilli in carriers is often rich and pure. 
Occasionally excretion is periodic. 



THE TYPHOID FEVERS 55 

As soon as the bacteriological diagnosis is made a further clinical 
diagnosis of the location of the focus is necessary. This involves 
examination of specimens from the duodenal contents if not al- 
ready made and cultures after ureteral catheterization in case of 
urinary carriers. A diagnosis of biliary passage lesion can be 
made if the duodenal contents are positive, but whether the focus 
is confined to the gall bladder or whether it also occurs in the 
liver cannot be told, except as a result of operation. An X-ray 
picture may assist in locating the lesion in a urinary carrier, as it 
is usually a unilateral pyelitis. 

A diagnosis of the kind of carrier should also be made, whether 
convalescent or contact, based on the history and probabilities of 
slight illness. The epidemiological significance of the carrier 
should also be looked into, such as history of occurrence of pre- 
vious cases among his contacts, and so forth. 

TREATMENT 

After a thorough diagnosis is made, further spread of bacilli 
should be prevented as far as possible by insisting on good personal 
hygiene of the carrier. If the carrier will not observe rules or is 
an old offender, quarantine may be enforced with legal sanction 
in many places. Under these circumstances the carrier is more 
apt to agree to radical treatment. 

In the technical treatment, surgical measures are the most 
effective. The focus in many carriers is a single local one which 
can be cured by excision. Thus many carriers have been cured 
by cholecystectomy and nephrectomy. Unfortunately, in some 
cases the foci are multiple, especially in the biliary tract and ex- 
cision of one focus does not cure the condition. Such carriers can 
be determined only by operation and are incurable at present, but 
probably form the minority. Cholecystectomy should, therefore, 
be tried in all cases possible. Cholecystectomy with hepatic drain- 
age has been advised for liver carriers. Illustrative specimens are 
given in figures 7, 8, and 9. 

The technical details of the operation cannot be discussed here, 
but the situation calls for cooperation on part of the surgeon. 
The diagnosis, made by the internist or pathologist, must be 
accepted without clinical evidence. Especial effort should be 



56 



CARRIERS IN INFECTIOUS DISEASES 



made not to damage the individual. In convalescent cases, 
operation should not be performed until at least six months after 
recovery, as some cases will spontaneously clear up during this 
interval. 






% 



Fig. 7. Gall Bladder and Gall Stone from a Typhoid Carrier Re- 
moved at Operation Seven Years after Original Attack 
Carrier was a member of the Army Nurse Corps. Operation cured the 
carrier condition. (Reprinted with permission from Journal of the Ameri- 
can Medical Association.) 

Many other methods of treatment have been tried and some 
partial success apparently has been obtained, but the results are 
so irregular, compared with those of surgical treatment, that 
coincidence may explain them. (See Chapter IV.) 



THE TYPHOID FEVERS 



57 




0. 







Fig. 8. Gall Bladder and Gall Stones from a Typhoid Carrier Re- 
moved at Operation Seven Years After Original Attack 
Carrier was an army cook who was detected by routine examination of 
food handlers. Operation did not cure the carrier state. 



58 



CARRIERS IN INFECTIOUS DISEASES 




< 

E-i 


.3 S 
o 


H 


QQ 


< 


2 c 
£ J 


Ph 


fa 


^ S 


H 


0) .2 


fa 

< 






P^ a 


fa 


CO += 


>H 


^ '2 

0) £ 


X 






73 T3 


02 


Pj o 


Ph 

fa 


C3 H-3 


^ .9 




'S 


« 


tj a 


Ph 


O a> 


■< 


° £ 


o 




Q 


'o . 


O 


d 


Ph 


C O 

.2 "■£ 


H 


+3 ce 


Eh 


.a £ 


h 


P3 


a ° 


<1 


8 >> 


« 




P 


g 2 


3 

O 


.9 3 
■go 


tf 


o 


fa 


fn 


Q 

fa 
> 

o 


!>> Ph 


o 

T3 *+h 


§ 


^ «, 


fa 


-4-5 ^ 
CO 


fa 


"d 3 


£ 




O 


co ^ 


M 


£ 03 


Eh 


o 


fa 


H? 32 


fa 




fa 


> o 


O 


fa 


o -*-' 


< 


K_ t t-l 

d ° 


W 


£ £ 


fa 


C3 ^ 


o 


d ;£ 


O 


c3 d 




CO ° 

03 CU , 
> ^h 


-1 


"" d j 


Ph 


*- a 


Q 


a? 


OS 


S*S 




u .s 


d 


,d 


£ 


* i 



THE TYPHOID FEVERS 59 

Gay, F. P. : Typhoid Fever. 1918, Macmillan Company. 

Gabbat, A. L. : Monographs of the Rockefeller Institute. 1922. No. 16. 

Nichols, H. J., Simmons, J. S., and Stimmel, C. O. : Jour. Amer. Med. 

Assoc, 1919, lxxiii, 680. 
Hbnes, H., Jb. : Jour. Amer. Med. Assoc., 1920, lxxv, 1771. 



CHAPTER VI 
Cholera 

Next to the discovery of the cholera vibrio in the intestinal 
tract of patients, the recognition of a chronic cholecystitis as a 
focus of the carrier state was the most important advance in the 
possibilities of control of this disease. The carrier conception was 
first reached in the study of cholera, but the practical consequences 
of this discovery were not generally realized until a pathological 
basis for the existence of carriers was established. Cholera in 
endemic centers occurs with distant seasonal regularity. There 
are intervals of complete freedom from the disease. The where- 
abouts of the vibrio in this interval was a mystery until a chronic 
cholecystitis was recognized. Much ingenuity was expended on 
possible life cycles in the environment, but, as is frequently the 
case in the infectious diseases, the trouble was found closer home. 
The carrier is now believed to be the real reservoir of the disease 
from year to year. While the acute case causes most other cases 
during an epidemic, the carrier causes the epidemic itself. The 
carrier problem in cholera is most difficult in endemic centers as 
the natives have racial and religious prejudices and personal 
habits which are foreign to scientific medicine. On the other 
hand, where bacteriological examinations and quarantine can be 
enforced, as in the case of emigrants, it has been shown by the 
Public Health Service that wholesale carrier work is possible and 
is effective in protecting the country from cholera. Most of the 
recent work in the prevention of cholera in India (Grieg) and in 
the Philippines (McLaughlin, Munson) has been along carrier 
lines. 

Incubationary carriers are known who pass vibrios in the stools 
for days or weeks and finally develop the disease. Digestive 
upsets from irritating food or catharsis may precipitate the 
attack. Such cases can be distinguished from contact carriers 
only by the outcome, as no test of immunity is available. 

As in the case of typhoid, the number of organisms in the body 
become rapidly reduced in most cases within the time of clinical 

60 



CHOLERA 61 

recovery. A small number, about 3 per cent, do, however, be- 
come convalescent carriers and reservoirs of infection. These 
carriers are apparently not as persistent as typhoid carriers, but 
final statements can not be made on this subject until more work 
is done on cultures of duodenal contents in life and on gall bladder 
contents at operation and autopsy. 

Contact carriers are still more temporary. They may be as 
numerous as 6 to 30 per cent. Care is necessary to rule out mild 
infections. 

PATHOLOGY 

As in the case of faecal typhoid carriers, a focus is found in 
the gall bladder. This consists of a mild catarrhal inflammation 
which gives no clinical symptoms and is discovered only by in- 
ference after bacteriological examination or at autopsy. It is not 
known whether lesions occur in other parts of the biliary system. 
Although the subject has not been as fully worked out as in typhoid 
carriers, the high percentage of positive findings in the bile strongly 
suggest that the cholecystitis is the principal carrier focus. 

There is no general agreement as to the pathogenesis of this 
lesion. Some observers favor the theory of ascending infection 
through the common duct, others (Greig), infection through the 
lymphatics. Cholera vibrios do not invade the blood to the same 
extent as typhoid bacilli, but they are not confined as strictly to the 
intestinal tract as was once thought, because they have been 
found in the urine during life and in the lungs at autopsy. A 
theory of portal system septicaemia with excretion of the vibrios 
through the bile has been advanced by the author to account for 
the cholecystitis. In any case, the lesion occurs and lasts for an 
indefinite time. Further work along these lines is much needed. 
An experimental cholecystitis can be reproduced experimentally 
in rabbits and especially in guinea pigs by intravenous injection 
or direct inoculation (Schobl). 

Carrier strains of the vibrio have been studied from the com- 
parative point of view and no differences have been noted as com- 
pared with strains from cases. Atypical strains, however, are 
especially apt to be troublesome. They may not agglutinate and 
their significance remains uncertain. 



62 CARRIERS IN INFECTIOUS DISEASES 

DIAGNOSIS 

The same general rules apply as in typhoid carriers. The 
final diagnosis is bacteriological, but the personal history and 
epidemiological circumstances may assist in the detection. Sero- 
agglutination may also be of value in some instances. 

Cultures of duodenal contents of suspected carriers have ap- 
parently not yet been made on any scale, but the information 
which can be gained in this way would be very valuable from 
many points of view. 

The specimens of feces are collected in the same way as in ty- 
phoid carrier work. As large numbers of persons must often be 
examined in a short time, an organization of the work is necessary. 

TECHNIQUE 

The principle of diagnosis is to isolate a vibrio which aggluti- 
nates with a specific serum. The special points, in the isolation, are 
the use of enrichment and a selective medium which favors the 
development of the vibrio and inhibits other organisms. A rectal 
swab or small amount of feces is enriched in alkaline peptone water, 
pH 8.4, for several hours. A transfer from the surface is then made 
to a second tube. After six hours the surface growth is spread 
on alkaline agar, pH 8.4 (faintly alkaline to phenolphthalein). 
This medium allows a good growth of the vibrios in translucent 
colonies. Material from the suspicious colonies is stained with 
dilute carbol fuchsin and examined for vibrios. If present, a 
micro-agglutination is made with standard anti-cholera serum, or a 
transfer is made to alkaline agar and a macro-agglutination is made 
the next day. If the reaction is clear cut, a diagnosis can be made. 
A transfer of the culture should be saved for confirmation. Some 
typical vibrios do not agglutinate well at first. Further cultural 
and serological work is necessary. There are many unsettled 
problems of strains of vibrios which apply to carrier as well as 
clinical work. No reliable virulence test is available. 

A great many differential and special media have been devised 
for cholera work. In general, the simplest is the best, and the 
above outline will give good results. 



CHOLEKA 63 

When carriers have been found, an effort should be made by 
the history and by further examinations to classify the carrier 
and to determine the social bearings of the condition. 

TREATMENT 

The first measure is isolation and instruction in personal hygiene. 
Intestinal upsets should be avoided as they may precipitate an 
attack in an incubationary carrier. Many carriers are relatively 
of short duration and will clear up while under observation. For 
chronic carriers, as in typhoid, many measures have been tried, 
but with irregular results. In long term chronic carriers, surgical 
measures should be considered. 

Greig. E. D. W. : Ind. Jour. Med. Res. 1913-4, i, 44, 59; 1914r-15, ii, 1, 28, 

907; 1916, iii, 259. 
Schobl, 0.: Phil. Jour. Sc, 1915, B., x, 11; Jour. Inf. Dis., 1916, xviii, 307. 
McLaughlin, A. J.: N. Y. Med. Jour., 1909, xc, 1116. 






CHAPTER VII 

The Dysenteries 

a. bacillary dysentery 

The carrier is apparently of less importance in the spread of 
dysentery than in the spread of typhoid or cholera. There are 
fewer true carriers and the individual carrier is less chronic and 
excretes fewer bacilli. Acute and chronic cases are usually re- 
sponsible for spreading infection. On the other hand, definite 
instances are recorded of spread of this serious disease through 
apparently healthy carriers. 

Incubationary carriers are known. In the absence of a test 
for susceptibility and in view of the relapsing character of the 
attack, it is difficult to diagnose such carriers except by careful 
consideration of the previous history and subsequent course. 

In temporary convalescent carriers, the curve representing the 
presence of bacilli in the feces falls gradually after clinical recovery, 
but does not reach a low percentage for about two months. Re- 
peated examinations are necessary to exclude the carrier state. 

Chronic convalescent carriers, running up to a year, occur in 1 
to 5 per cent in different series. It is difficult to draw the line 
between relapsing carriers and chronic cases. Flexner bacillus 
infections are more apt to result in carriers, while Shiga bacillus 
infections are more apt to be chronic cases. 

Contact carriers have usually been considered as rare, but with 
improvement in technique of examination, are found more fre- 
quently. Here again the exact diagnosis is difficult between a 
convalescent carrier after a mild case and a true contact carrier 
who has never been sick. 

Pathology 

In the true contact carrier the bacilli apparently have no focus 
and live for a short time in the lumen of the colon. 

64 



THE DYSENTERIES 65 

In the convalescent carrier the lesion is an ulcer of the original 
attack which has failed to heal with the establishment of a general 
immunity. The ulcers of bacillary dysentery have characteristic 
differences from amoebic ulcers. They usually run transversely, 
are superficial and occur in the ileum as well as the caecum. 
Dysentery bacilli apparently do not regularly invade the blood 
and other foci, as in the gall bladder, are rare. Urinary carriers 
are unknown. 

Diagnosis 

The personal history of intestinal trouble and of residence in 
infected regions may be suggestive. The presence of mucous in 
the stool is suspicious. Epidemiological data are also often useful. 

In the laboratory diagnosis, the finding of the organism is of 
course the main object, but examination of the blood serum for 
agglutination may be of much assistance and sometimes a pre- 
sumptive diagnosis must be made on agglutination alone. The 
agglutination curve usually falls promptly after convalescence 
and its persistence in strength up to 1-50, or 1-100 is very sus- 
picious, especially in view of the difficulties of stool examination. 

Technique 

The general rules given for the examination of feces of suspected 
typhoid carriers apply here. Examination of the rectum with a 
protoscope sometimes reveals an ulcer which can be cultured 
directly. In the stool mucous should be sought for and plated 
on several plates. A great many media have been used. Lactose 
litmus agar is one of the simplest and best. Endo medium should 
be used, but is not favourable for the growth of the Shiga bacillus. 

The plates after incubation are examined for non-lactose fer- 
menting colonies and transfers are made to Russell double or 
triple sugar in the regular way. The reactions in the Russell tube 
are identical with those of typhoid bacillus. There is an acid 
butt with no bubbles of gas and an alkaline slant. If typical 
growths in the tubes show on staining a Gram negative bacillus, 
agglutination is done with monovalent sera at a strength corre- 
sponding to the titre. There are a number of organisms whose 
significance in actual dysentery is uncertain and the same is true 



66 CARRIERS IN INFECTIOUS DISEASES 

in carrier work. If an organism is isolated it should be aggluti- 
nated with the individual's serum for additional data. A nega- 
tive reaction would tend to rule out a convalescent carrier, but not 
a contact carrier. At least three release cultures should be made 
over two or three weeks as the bacilli are hard to find. 

Treatment 

The field of specific treatment with serum vaccines has not been 
thoroughly explored, but is not promising. If the ulcer is in the 
rectum alone local treatment is effective. Usually the most that 
can be done is general hygienic treatment with lavage of the 
colon. Instruction in personal hygiene should be given. Con- 
tinued observation is necessary. 

Medical Research Committee. London, Special Reports Nos. 7 and 40. 
B. PROTOZOAL DYSENTERIES 

1. Amoebic dysentery 

The pathogenic amoeba, Endamoeba histolytica, is not limited 
to the tropics as closely as was formerly thought and amoebic 
dysentery, or more properly amoebiasis, is a serious cause of ill 
health in many parts of the world. Amoebiasis is the better 
term as dysenteric symptoms may be slight or absent and the 
principal damage may be anemia, neurasthenia, or liver abscess. 
In the spread of this infection carriers play an important part. 
In fact, the cyst, which is the only infecting stage in the life cycle 
of the amoeba, is characteristic of carriers rather than of cases, 
as its presence indicates that a balance is being reached. The 
vegetative forms, which produce the symptoms, are not infective. 
From the point of view of the parasite, therefore, the transmission 
of the disease is due to a carrier stage in 100 per cent of instances. 
In the acute stages of the infection, cysts are not found as fre- 
quently as in the chronic stages. It may be difficult at times to 
differentiate a chronic case from a true carrier, as cases merge into 
carriers and carriers into relapsing cases; but true carriers do 
exist, with a limited active focus and many cysts. The immunity 
in such protozoal diseases is not as clear cut as in bacterial diseases. 
A balance is more easily reached and with less evidence of infection. 



THE DYSENTERIES 67 

The percentage of temporary convalescent carriers is very 
high. On the Mexican border in 1916-1917, Craig found that of 
115 cases, 86, or about 75 per cent, developed cysts and became 
at least temporary convalescent carriers. The further history of 
such carriers is not entirely known. Spontaneous cure of some 
cases and carriers undoubtedly occurs, but even with the best 
treatment about 10 per cent may remain carriers. The percent- 
age of so-called contact carriers is said to be much more numerous 
than convalescent carriers, but the possibility of a mild or atypical 
attack is to be kept in mind. In the general population, carriers 
are of course most prevalent in endemic centers in the tropics and 
least in temperate regions. Thus, Young, in Manaos, Brazil, 
found no less than 27.5 per cent of native troops, apparently in 
good health, harboring cysts of Endamoeba histolytica, whereas 
among army recruits in England, Mathews and Smith found only 
5.6 per cent carriers. The possibilities of carrier infection through 
food handled by careless and ignorant native servants have often 
been realized. 

Pathology. In the chronic convalescent carrier the lesion is an 
unhealed ulcer of the colon. Here the vegetative forms of the 
parasite persist and produce cysts. This cyst cannot reproduce 
itself and the vegetative form cannot live long in the intestinal 
contents. It requires some focus or home in the intestinal wall. 
Hence, the pure contact carrier is very temporary. So-called 
chronic contact carriers are either mild chronic cases or convales- 
cent carriers from mild infections. 

Chronic foci occur in other parts of the body, as abscesses, but 
usually have no natural outlet. One case of gall bladder lesion has 
come to the writer's notice. The patient, a medical officer, had 
an enlarged gall bladder and incidentally was an amoebic carrier. 
The gall bladder on removal had a thick leathery wall. The 
contents were purulent and showed many active amoebae. Amoe- 
bae were also found later in the wall by section. Soon after opera- 
tion he was free from the carrier state. This condition is possibly 
not as unusual as it seems. 

Diagnosis. This is made by the microscope. No serological 
reactions are available. Clinical history and circumstances may 
be suggestive. A formed stool is preferable for looking for cysts. 



b» CAERIERS IN INFECTIOUS DISEASES 

Frequently a diagnosis can be made with the fresh specimen by- 
finding of four nucleated round or oval cysts. In general, how- 
ever, on account of the frequent presence of other ; cysts in the 
feces, it is preferable to have stained specimens examined by an 
experienced worker. Differentiation must be made from cysts 
of the harmless amoeba and those of other protozoa. Occasionally 
material can be obtained directly from a rectal ulcer. A single 
examination will detect only about one-third of carriers. 

In the examination of large numbers of individuals, which must 
be made if the carrier program is to yield results, some organiza- 
tion is necessary. Specimens must be properly collected, labelled, 
and so forth, as was emphasized under discussion of specimens 
for typhoid carriers. 

Treatment. The treatment is that for the original infection and 
must be directed both against the vegetative forms in the tissue 
and the cysts in the feces. Emetin is best for the tissue infection. 
Hypodermic injections in courses are given of \ to 1 grain a day 
for seven days with a short rest and repetition. Toxic symptoms 
must be watched for such as neuritis, especially of the legs, and 
myocarditis. The cysts in the feces can be reduced by large doses 
of bismuth subnitrate, one heaping teaspoonful in one-half glass 
of water before meals. Emetin bismuth iodide by mouth has 
advantages in both directions, but it is apt to nauseate. Courses 
of 3 grains daily for twelve days cured 91 per cent of cases in the 
English experience. Colon lavage with quinine 1 : 1000, or argyrol 
is of value. 

Repeated negative examinations are necessary for release as 
single examinations are inadequate. 

Carriers should be instructed in personal hygiene and kept 
in quarantine if not too numerous. If the number is too large 
for quarantine, personal hygiene and sanitation must be depended 
on. 

2. Other protozoal dysenteries 

True carriers are definitely known in one other form of proto- 
zoal dysentery, namely, Balantidiosis. The disease is compara- 
tively rare. The carrier relationships are much the same as in 
amoebiasis. The vegetative forms live in ulcers in the wall of the 



THE DYSENTERIES 69 

intestine and form cysts which are excreted and are infective. It 
is possible that the vegetative forms can live some time in the 
feces and encyst there. If this is so, true contact carriers would 
have more of a place than in amoebic dysentery. The pig, a 
common scavenger in the tropics, is infected with a similar 
parasite. 

Emetine and arsphenamine should be tried in treatment. 

Besides these true carriers, there are a large number of possible 
carriers of other protozoa, such as trichomonads, lamblia, et 
cetera, whose clinical significance is not yet well understood. They 
may be primarily pathogenic in some cases, or they may be purely 
secondary or saphrophytic. Giardia intestinalis is generally re- 
garded as pathogenic, but there is considerable doubt about the 
importance of other protozoa. The carriers of most of them are 
probable pseudo carriers. 

In all these conditions, with the possible exception of tricho- 
monas infections, the cyst stage of the parasite occurs as the basis 
of a possible carrier state. 

In Giardia infections, it is often difficult to differentiate a case 
from a carrier as the symptoms in a case may be mild and indefinite. 
The lesion is in the duodenum where the parasites become at- 
tached to the mucous membrane. True carriers are either immune 
or slightly infected. 

The diagnosis is made on the absence of definite symptoms and 
the finding of cysts in the intestinal contents. The duodenal tube 
has been used to good advantage as motile forms have been found 
in duodenal contents when the feces were negative or showed 
only a few cysts. 

The diagnosis of carriers of intestinal protozoa requires con- 
siderable experience and technique. A large number of cysts 
or cyst-like bodies occur in feces and frequent errors in interpre- 
tation have been made which vitiate many diagnoses and sets of 
statistics. 

Medical Besearch Committee. London, Special Reports Nos. 4, 15, 29. 
Dobell, Clifford, and O'Connor, F. W. : The Intestinal Protozoa of 

Man. Wm. Wood & Co., 1921. 
Craig, C. F. : Military Surgeon, 1917, March and April. 



CHAPTER VIII 

Helminthoses 

Carriers of helminths are recognized and play a definite part 
in the spread of diseases due to worms. They are not dangerous 
to their immediate contacts, like the intestinal carriers so far 
considered, as the parasites must develop outside the body before 
infection is possible. The carrier, therefore, infects only his 
environment and is most important in warm parts of the earth 
where the population lives close to the soil. 

In these infections it may be especially difficult to distinguish 
between cases and carriers. A person may become immunized to 
the effect of the parasite and thus be a true carrier, but usually 
a carrier is one who has not enough parasites to be a case. Thus, 
in hookworm infections, the number of worms necessary to pro- 
duce any real disease is put at 10 to 100 or more by different 
authors. A person with a few worms would thus be a carrier. 
While from the theoretical standpoint it is very desirable to have 
well defined standards of cases and carriers, it is a mistake, from 
the practical point of view, to split hairs over the diagnosis. 

While carriers usually infect their environment less than cases, 
a continued small infection will in time be as bad as a single mas- 
sive infection. 

Carriers in hookworm infections will be described as typical of 
this group because this infection is best known and other less well 
known diseases seem to be similar in general. 

Carriers are very prevalent in infected regions. A large per- 
centage of persons excrete ova but only a few will show symptoms. 
Hence, the carrier is a real problem. 

PATHOLOGY 

The carrier lesion is the same as the case lesion. The worms 
attach themselves to the mucous membrane of the ileum and 
feed on bits of tissues and tissue juices. Their number is so small, 
however, that they do no general damage. They may live for 
a time free in the lumen like other round worms. 

70 



HELMINTHOSES 71 

DIAGNOSIS 

Residence in an endemic area is suggestive and history of ex- 
posure to skin infection or of ground itch may be obtained. Ex- 
amination of blood for eosinophilia may also be suggestive. The 
final diagnosis depends on finding ova or worms in the stool. 

It has been found that the number of ova in the stool is roughly 
an index of the number of worms present. If we, therefore, adopt 
as a standard of carrier state, 10 to 100 worms, the condition can 
be diagnosed by less than one ovum per 100 fields. 

The diagnosis may be made by direct examination of the stool, 
but concentration methods are much better on account of the 
scarcity of ova. The brine method of Barbour was found most 
useful for examination of large numbers of men during the war. 
The feces were mixed with equal parts of a hypertonic salt solu- 
tion in a small container such as a salt cellar or pill box and allowed 
to stand a few minutes. The eggs float to the top and will attach 
themselves to the under side of a slide placed over the surface. 

TREATMENT 

This is the same as for a mild infection. Carriers can be cured 
by a course of thymol, oil of chenopodium or carbon tetrachloride. 
If possible, the stool should be strained and worms counted. Sub- 
sequent examination will tell results of treatment. 

In general management, carriers must be considered in same 
class with cases, and feces should be disposed of so that soil will not 
be infected. As the cure is so easy, no hardships on the individual 
are necessary. 

Smillie, W. G.: Am. Jour. Trop. Med., 1921, i, 389. 



CHAPTER IX 
Diphtheria 

It is generally accepted that diphtheria is largely kept in exist- 
ence by chronic carriers who act as reservoirs and furnish the 
bacilli at favorable seasons to susceptible individuals. If it were 
not for carriers the disease would be much less of a problem. On 
the theoretical side the control of carriers has been carried nearly 
to a stage of perfection. The possible carrier can be diagnosed 
with comparative ease. The virulence of the suspected organism 
can be determined with considerable certainty. The susceptibil- 
ity of possible hosts can also be determined and the treatment of 
the carrier is fairly effective. Hence, theoretically we are in a 
very favorable position to stamp out this disease along carrier 
lines. Practically, however, the program usually breaks down 
because it is too big. The number of exposed and susceptible 
persons is usually large. The laboratory and clinical facilities are 
usually limited. Only a certain number of cultures can be ex- 
amined in a day and only a much smaller number of virulence 
tests can be made. Only a certain number of Schick tests can be 
made and several days' observation are needed. Only a certain 
number of persons can be quarantined or held under observation. 
The result is that the purely bacteriological line of attack fails and 
common sense governs as it should. Clinical cases are considered 
first and as much carrier work is done as is feasible. As labora- 
tory facilities increase, more is accomplished along these lines, 
but it is doubtful if carrier work alone can be sufficiently well done 
to produce a radical effect on the prevalence of diphtheria. The 
most promising results are being obtained by a combination of 
case work, carrier work and active immunization of Schick positive 
children. The toxin antitoxin treatment seems to give a high and 
lasting immunity and the most practical objective is to produce 
a large number of immunes along with a reduction of the foci of 
infection. The immunization program is not sufficient alone as 
the reactions among adults are too severe for general practice. 

72 



DIPHTHERIA 73 

However, the fear of producing a large number of carriers among 
immunized children is groundless, as these contact carriers are 
temporary. The worst carriers are the chronic convalescent ones. 

Incubationary carriers. These carriers can be recognized and 
play some part in the dissemination of bacilli, but the incubation 
period is so short and the diagnosis of a virulent organism in a 
Schick positive individual requires so much time that the incuba- 
tionary carrier cannot be assigned a very definite place in carrier 
work. If they are found, however, they should be treated like 
cases. 

Convalescent carriers. With convalescence the bacilli begin 
gradually to disappear and, by the end of a month, 85 per cent of 
convalescents are bacteriological recoveries. By the end of a 
second month, 98 per cent are free. The remainder pass into the 
most dangerous class of more or less chronic carriers. Foreign 
bodies or deformities in the nose and throat predispose to the 
chronic carrier state. Release cultures made during early con- 
valescence are examined only morphologically. Virulence tests 
are not necessary as it has been found (Wadsworth) that 90 per 
cent of strains from convalescent carriers are virulent up to three 
months after recovery. 

Contact carriers. Pure contact carriers occur among attendants, 
families and contacts of cases and carriers in from 10 to 20 per cent 
of instances. The organisms are virulent in 80 per cent of in- 
stances, and the carriers are dangerous, but the condition is tem- 
porary unless there is some predisposing deformity of a chronic 
focus. These carriers are immune or Schick negative. 

In the general population true carriers of virulent organisms 
are less than 1 in 1000. Among children, however, 2 per cent are 
true carriers. Only 10 per cent of non contact or non convalescent 
carriers show virulent organisms. 

Possible and pseudo carriers. In any extensive carrier work a 
number of individuals will be found who are carrying organisms 
which morphologically resemble true virulent diphtheria bacilli. 
A preliminary tentative diagnosis must be made pending further 
examination. Virulence and cultural tests show that many of 
these organisms are diphtheroids or non-virulent diphtheria 
bacilli. The final diagnosis should be made of pseudo carrier and 



74 CARRIERS IN INFECTIOUS DISEASES 

the individual should be released from observation. No long 
term quarantine should be carried out, as has been done, on 
morphological grounds alone. 

PATHOLOGY 

The focus in incubationary carriers is at the site of the com- 
ing lesion, usually in the throat near the tonsils and consists in the 
first stages of invasion. The number of organisms is probably 
large. 

In the contact carrier there is either no lesion or a nonspecific 
one due to some other cause such as a foreign body or a deformity 
on which the bacilli become engrafted. The lesion then comes 
to resemble that of a convalescent carrier. 

Chronic convalescent carriers. The tonsil is most frequently the 
focus in the chronic convalescent carrier and may be taken as 
typical. Other similar foci may exist in the adenoids or sinuses, 
but the tonsil is most frequently and longest infected. The crypts 
have a local diphtheritic inflammation of their walls. The lining 
epithelium is disintegrated and replaced by inflammatory tissue 
which pours out an exudate into the crypt and on the surface of 
the tonsil (fig. 1). There is a characteristic fibrinous exudate in 
the lesion. The diphtheria bacilli are easily found in sections and 
are clearly out of reach of surface disinfection (fig. 10). These 
carriers have a general but not a local immunity. The general 
immunity may be carried over from the disease or it may be con- 
stantly produced by the small carrier lesion which acts as 
a vaccination. 

DIAGNOSIS 

Suspected diagnosis may be made on epidemiological or clinical 
grounds, and a clean tonsillectomy is evidence against the carrier 
state, but the final diagnosis is bacteriological and the presumptive 
laboratory diagnosis is relatively so simple that wholesale cultures 
are usually made without regard to clinical or epidemiological 
probabilities. If Schick tests have previously been made on any 
of the suspects, the results should be obtained. 

The specimen. A sterile swab should be pressed on each tonsil 
and passed over the faucial entrance. Repeated examinations in- 



DIPHTHERIA 



75 



crease the percentage of positive results. Nasal specimens ob- 
tained by passing separate swabs through each side of the nose to 
the nasopharynx, also reveal additional carriers. Nasal obstruc- 
tion may interfere with free passage of the swab, but may be the 




Fig. 10. Diphtheria Bacilli in Tonsil of a Convalescent Carrier 

Three Months After Attack. Higher Magnification of 

Previous Photograph (Fig. 1). X 1000 

Diphtheria bacilli in the walls of the crypts. Bacilli cultivated from 
this tonsil were virulent for guinea pig. 

predisposing cause of the infection. The swab should be immedi- 
ately passed over the surface of coagulated blood serum in a 
tube or box or plate and incubated, or the swab be sent to the labo- 
ratory and inoculated there. The organisms resist drying and low 



76 CARRIERS IN INFECTIOUS DISEASES 

temperature, but speed is an object. Direct smears from the 
throat are not as useful in the diagnosis of carriers as they are in 
some cases. 

While the culture is incubating Schick tests should be started, 
if possible, by the intracutaneous injection of 0.2 cc. of 50 m.l.d. 
of toxin for a guinea pig of 250 grams with a control of toxin heated 
to 75° for five minutes. 

Usually the incubation is carried on for over night but shorter 
incubation gives positive results in some cases. Incubation for 
48 hours is said to increase positive results by about 10 per cent. 
Smears are made from suspicious colonies or from the mass growth 
and are stained by alkaline methylene blue, Gram's or Neisser's 
stain. The presumptive diagnosis is made on morphological 
grounds. No special morphology of carrier strains is recognized. 
Doubtful findings should be checked by further specimens and 
more detailed examination. Meanwhile possible carriers should 
be quarantined. If the carrier is an early convalescent or contact 
carrier, a virulence test is not necessary as most of these strains 
are virulent. But if the carrier state is long continued or of doubt- 
ful origin, virulence tests must be made. 

TECHNIQUE 

It is of course most satisfactory to isolate the organism in pure 
culture, but in view of the large number of cultures to be tested 
a rough test may be more serviceable. The slant from which the 
diagnosis was made is washed off in 2 cc. NaCL and 1 cc. injected 
subcutaneously in a guinea pig. If the pig does not die in three 
days it may be concluded that the culture is avirulent. If the 
pig dies with characteristic injection oedema of the site of inocula- 
tion and with hyperaemia of the adrenals it may be concluded that 
the culture is virulent. Too often, however, the pig dies with 
indefinite evidences and it can not be decided whether the animal 
died of diphtheria intoxication or mixed infection. 

A pure culture is obtained by emulsifying material from the 
original tube in broth and spreading a loopful well over a blood 
agar plate. Locffler plates may be used, but are more trouble- 
some to make and are not much superior. Single suspected colonies 
arc fished and stained and if positive morphologically arc trans- 



DIPHTHERIA 77 

ferred to broth or to a Loeffler or blood agar slant. After forty- 
eight hours 1 cc. of the broth culture of a virulent organism should 
kill a pig in three days. If the slant is used it is washed off and 
one-half is given. As a control, a guinea pig may be injected with 
the same dose and immunized with 500 units of antitoxin, but 
ordinarily this is not necessary. It is more economical to use the 
intracutaneous method by which a number of tests can be made 
on the same animal, but more experience and skill are necessary. 

When a carrier is found an attempt should be made by regional 
cultures to locate the focus. Usually both tonsils are infected but 
the infection may be in one or in one side of the nose. 

There are now several possibilities. The patient may have a 
virulent organism and a negative Schick test — he is a true carrier, 
contact or convalescent. The history may decide which. He 
may have a non-virulent organism and a negative Schick test; 
he is a pseudo carrier. He may have a virulent organism and a 
positive Schick test; he may be an incubationary carrier or early 
case and should have antitoxin. He may have an avirulent or- 
ganism and a positive Schick test, he is a psuedo carrier, but toxin 
antitoxin treatment should be considered. 

As was said before, in trying to handle large numbers of cases, 
as in schools or troops, this ideal scheme usually breaks down and 
common sense rules, that is, cases are given priority and carriers 
are considered if possible. 

TREATMENT 

Many carriers clear up by themselves in time. Release cul- 
tures should be continued. For the resistant cases, many lines 
of treatment have been proposed, but excision of the focus by 
tonsillectomy is the most effective except in the rare cases when the 
lesion is elsewhere. On the specific side, antitoxin does not affect 
the bacteria. An antibacterial serum has been made and used as 
powder for use by insufflation. Cures have been reported, but 
cures have also followed the use of powdered meningococcus 
serum. The effect is probably a non-specific inflammatory reac- 
tion. Insufflation of kaolin also acts in the same way. Attempts 
have been made to implant lactic acid bacilli and staphylococci. 
The former is ineffective, the latter dangerous. Every sort of 



78 CAKKIERS IN INFECTIOUS DISEASES 

antiseptic has been proposed. The most reasonable are silver 
nitrate, 10 per cent, and iodine, 2 per cent in glycerin. If these 
antiseptics are applied actually to crypts they may succeed in 
some cases; but this procedure requires more care than is usually 
available and the crypts have underground communications. It 
is simpler and more effective to remove the tonsil. This operation 
however, should not be done until several months after the disease 
in order to avoid the complication of endocarditis. 

X-ray treatment of the tonsil has been proposed and is prefer- 
able in some cases. Several treatments are necessary. The 
action is to shrink up the lymphatic tissue and improve nutrition 
and drainage. There is no antiseptic effect. 

In cases which resist tonsillectomy, correction of other foci 
possibly in sinuses and irrigation of nose and throat with saline is 
indicated. 

Isolation. Carriers of virulent bacilli should be isolated. 
Appropriate treatment for the kind of carrier should be carried out. 
For release, three successive negative cultures should be required 
at daily intervals without any local treatment. No protracted 
isolation should be imposed unless the organisms are proved to be 
virulent. 

Wadsworth, A. B.: Jour. Amer. Med. Assoc, 1920, xlvii, 1633. 
Weaver, G. H.: Jour. Amer. Med. Assoc, 1921, lxxvi, 831. 
Spooner, L. H.: Jour. Amer. Med. Assoc, 1920, lxxiv, 582. 
Keefer, F. R., Friedburg, S. A., and Aronson, J. D.: Jour. Amer. Med 
Assoc, 1918, 1206. 



CHAPTER X 

Epidemic Meningitis (Meningococcus Infection) 

Next to diphtheria carriers, carriers in meningitis have the most 
definite place among the respiratory diseases. The experiences of 
the war brought the carrier aspects of the disease especially into 
prominence. It is probably more exact to speak of meningococcus 
infections than of meningitis, because apparently there may be a 
local infection in the nasopharynx and a blood infection without 
true meningitis. The carrier is recognized as an essential part in 
the continued existence of the disease. The case is generally 
too sick to spread the germs extensively, while the carrier is free 
to do so. On the other hand, the radical control of the disease by 
carrier work alone is generally considered impossible on account 
of technical and administrative difficulties. Our insufficient 
knowledge of virulence and immunity also weakens a radical 
carrier attack. English experience has also apparently shown 
that increasing the air space is usually effective in controlling the 
disease among troops. Carrier work, therefore, tends to be 
confined to convalescents and immediate contacts and is com- 
bined with other general measures. 

The object of the carrier program is of course to prevent a 
virulent organism from reaching a susceptible individual. In the 
problem of the meningococcus infection, we have no simple clinical 
method of determining either the virulence of the meningococcus 
or the susceptibility of the host. Such bacteriological and clinical 
work as has been done on the subject indicate the following situa- 
tion (Heist). Strains from the throats of carriers are not as viru- 
lent as strains from the spinal fluid of cases. Some carrier strains 
are more virulent than others. Not over 5 per cent of persons are 
susceptible to carrier strains. The results seem to throw some 
light on the epidemiology of meningitis and may explain the dif- 
ference between the seriousness of the case and the relative harm- 
lessness of the carrier. 

Incubationary carriers exist and constitute about 0.5 per cent 
of all carriers. Convalescent carriers number up to 5 per cent for 

79 



80 CARRIERS IN INFECTIOUS DISEASES 

three months after convalescence and occasionally much longer. 
Contact carriers are more temporary, but more numerous. Some 
surveys made during the war ran very high with but very few cases. 
In the general population the percentage is about 3. As we have 
no simple test for virulence and immunity, the only logical carrier 
method of attack would be to examine all concerned and to isolate 
those carrying either of the two recognized types of meningococci. 
The amount of technical and administrative work involved usually 
defeats such a plan. 

Special mention should be made of one feat during the war in 
which the entire 89th Division of 40,000 men were cultured for 
carriers. This was done under the direction of Lieutenant- 
Colonel E. H. Schorer at Camp Funston, Kansas. The Division 
Surgeon was Colonel J. L. Shepard, M.C., U. S. A. The men came 
from an endemic area of meningitis and in spite of the ordinary 
measures, cases continued to appear. It was decided to examine the 
entire division for carriers and this was accomplished in about six 
weeks, by using six officers as swabbers and nine officers in the 
laboratory while the enlisted men worked in day and night shifts. 
About 3 per cent of carriers were found. Altogether during the 
winter of 1917-1918, 102,170 cultures were made and 3290 carriers 
were detected and removed from their organizations. Meningitis 
ceased to be a problem when the work was accomplished. The 
results have been criticized on the ground that such mass work is too 
crude technically. Some evidence on this point is seen in the fact 
that out of a total of 152 cases of meningitis, 16, or over 10 per cent 
occurred in incubationary carriers who had been already detected 
by the survey. The removal of these men alone diminished the 
exposure rate by 17 per cent. 

At the outbreak of the war, the expert advisors recommended 
general carrier work. When the technical difficulties of applying 
these measures on a large scale were realized, carrier work became 
limited to convalescents and immediate contacts. But the work 
at Funston showed that success in phorology depends largely on 
the energy and determination of the individuals concerned rather 
than on the official program. If the laboratory facilities are or can 
be made adequate and if the circumstances are sufficiently urgent, 
carrier work should be more and more extensive. 



EPIDEMIC MENINGITIS 81 

PATHOLOGY 

Comparative regional cultures show that the principal carrier 
focus is in the vault of the nasopharynx. No conclusive patholog- 
ical studies of the lesion are available. It is usually believed that 
the meningococci live superficially in the crypts of the mucous 
glands. A large amount of mucus is thought by many observers 
to indicate the carrier possibility. But in some instances the menin- 
gococci inhabit the epithelial barrier without marked disturbance. 
Predisposing conditions are found in other lesions, especially 
deformities of the nose and lymphoid overgrowths. Some car- 
riers show meningismus with a normal spinal fluid. 

DIAGNOSIS 

The diagnosis can sometimes be suspected on clinical and epi- 
demiological grounds from the personal history and evidence of 
nasopharyngeal trouble. Skin tests with bacterial powder or 
solutions have not been specific enough to pick out carriers. The 
agglutination test is occasionally valuable. 

The bacteriological diagnosis requires special care in securing 
and handling of the specimen, as the organisms lie in a protected 
position and are especially fragile. 

A good nasal swab is sufficient, the more elaborate West swab 
being unnecessary. The most open side of the nose should be 
entered and the swab pushed to the back wall of the nasopharynx, 
then rotated and withdrawn. 

The specimen should be kept warm and moist until the media 
is inoculated. The media must also be kept warm after inocula- 
tion. The English in the war devised special warm containers to 
carry specimens in. Whole or laked blood media is most con- 
venient, but any serum enriched medium can be used. The 
specimen is planted first on a small surface at the edge of the 
plate, then with a sterile loop the plate is streaked radially. 
Schorer put several cultures on the same plate. After incubation, 
typical colonies are picked and stained and Gram negative cocci 
are selected for further work. They are transferred to other 
media for macro-agglutination or in some instances may be ag- 
glutinated microscopically with polyvalent and normal and para 



82 CARKIERS IN INFECTIOUS DISEASES 

type sera. No diagnosis of a true carrier should be made except 
with type identification. 

The following extracts are made from the Standard Technique 
of Meningococcus Carrier Detection issued by the Medical De- 
partments of the Army, Navy and Public Health Services during 
the War: These directions were prepared by a committee of 
specialists whose chairman was Col. F. F. Russell, in charge of 
the Division of Infectious Diseases and Laboratories of the Surgeon- 
General's Office, U. S. Army. 

I. CULTURING. 

a. Wherever possible the cultures should be taken in a small 

room in the regimental infirmary. The floor of this room 
should be washed with an abundance of soap and water 
one hour before the men enter for culture, and should be 
wet during the process of culturing. 

b. Only a few men at a time should be admitted to the culture 

room. 

c. Windows and doors should be closed all the time. 

d. Cultures should not be made within an hour after meals. 

e. No men should be examined on the same day on which they 

are sprayed. 
II. Method of Swabbing. 

a. The swab used should be : 

1. A naked wire 25 cm. long, with a small absorbent cotton 

pledget on one end, well covering the end of the wire, 
and a ring handle on the other. The wire should be 
flexible, such as stove pipe wire or hay baling wire, 
of about 18 gauge. The swabs may be sterilized in 
glass or paper containers in groups of 5-20. The last 
1 to 2 cm. of the pledget end of the swab is bent to an 
angle of about 30 to 40 degrees. This swab is simple 
and has proved most satisfactory, and can be at once 
discarded. 

2. West Tube. This gives satisfactory cultures, but is 

cumbersome, and not strictly necessary. 

3. Straight unprotected nasal swab. This is useful in the 

case of individuals with highly irritable throats, but 
, is not recommended as a routine. 

b. The subject should be seated facing the light. Tongue depres- 

sors are to be used when necessary. The swab should be 
passed behind the soft palate while the subject is phonat- 
ing. The swab, having passed up behind the palate, is 
introduced successively into each posterior naris, and then 
is drawn across the posterior wall of the naso-pharynx. 



EPIDEMIC MENINGITIS 83 

The swab is then withdrawn, taking care not to touch the 
throat surfaces or the tongue; this is best accomplished 
during phonation. The success of carrier search depends 
largely on the care with which the swabbing is done, hence 
the man taking the cultures should be able to execute these 
directions skilfully. He should be either a nose and 
throat specialist, the bacteriologist himself, or directly 
under the latter's supervision. 

III. Method of Inoculating Plates. 

a. The mucous charged swab should be applied over a limited area 

at the periphery of the plate. From this the spread is 
made by a wire loop passed by a series of radial strokes, 
each starting from the infected point. If there is very 
little mucus it is often possible to smear directly from the 
end of the swab. 

b. A single person per 10 cm. plate is preferable. More than two 

cultures on one plate should never be made. 

c. The plate must be inoculated while warm and kept warm until 

replaced in the incubator. To accomplish this, sterile 
plates already warmed by storage in the incubator, should 
be packed in a device insulated against the loss of heat, 
such as a fireless cooker, for transportation. 
Care should he taken to keep the plates warm during the inocu- 
lation process. It is advisable to carry a plate seeded 
with known culture of meningococcus to act as control. 

IV. Culture Medium. 

a. Standard nutrient 2 per cent agar. (Beef infusion, or Liebig's 

beef extract, 0.5 per cent NaCl, 1 per cent peptone, Fair- 
child's or Difco; reaction; plus 0.5, phenolphthalein.) 
Dextrose is not necessary. A convenient method of 
storage is in 200 to 300 cc. quantities, in flasks of sufficient 
size to permit of the addition and mixing of the following : 

1. Defibrinated blood — human, horse, sheep, goat, or rabbit 

— about 1 to 10 cc. of agar. 

2. Laked blood. (Blood, 1 part; distilled water, 3 parts; of 

this mixture add 1 to 10 cc. of agar.) Both these 
blood preparations should be stored ready for use in 
the ice box. They are good as long as they remain 
uncontaminated, and the whole blood unhaemolysed. 
They should be added to the agar only when the 
latter is at a temperature of 45° to 50°C. 

b. Starch agar is suitable for stock cultures, and for mailing 

cultures. 

c. Plates should be incubated, inverted) over night before use, 

to insure sterility. 



84 CARRIERS IN INFECTIOUS DISEASES 

V. Examination of Inoculated Plates. 

a. Plates should be inverted when placed in the incubator. 

b. Plates will be ready for examination after twelve to eighteen 

hours' incubation at 37.5°C. 

c. Discard all plates that are crowded and do not show discreet 

well separated colonies. 

d. The meningococcus colony on the whole blood medium does 

not produce green coloration or haemolysis. It tends to 
be somewhat larger than the streptococcus and pneumo- 
coccus. The colonies are moist, elevated, outlines are ill 
defined, and on moderately opaque blood agar have a 
faintly bluish tint. The colonies are not usually opaque, 
a characteristic which distinguishes them from the staphy- 
lococcus. 
On transparent blood medium and with transmitted light under 
lens magnification the colony may be nearly clear, but often 
shows a very faint smoky gray-blue quality. This charac- 
teristic is intensified by passing the finger between the 
light and the colony to shade it. Further lens effect may 
be seen by moving the plate so that the colony passes 
across some distant obstruction to the light as a string 
stretched across the window. The colony is never granu- 
lar, in young cultures. 
The colony should be confirmed by smear and Gram stain. 
VI. Teansplantation. 

The suspected (ringed) colonies are transferred to warmed moist 
blood agar slants. They must have been incubated to insure 
sterility. It is best to keep the tubes continuously in a warm 
water bath until finally placed in the incubator. If transfers 
are made under these conditions there will be enough growth 
for identification in about eight hours. 
Two essentials to success in growing meningococci are moist 
media, kept constantly from the time of inoculation at body 
temperature. 
VII. Identification. 

a. Microscopic. Smear preparations are made in the usual 

way stained by Gram. The presence of a few gram posi- 
tive, or other contaminating organisms does not make the 
culture unsuitable for agglutination. 

b. Agglutination. All Gram negative micrococci are subjected 

to agglutination in the following way: 
The serum dilutions are first set up, and the bacterial emulsion 
is made directly in them. To make this emulsion a loop- 
ful of the suspected culture is scraped off, and the loaded 
wire is passed well down the tube almost to the level of the 
fluid. The bacterial mass is then rubbed off against the 



EPIDEMIC MENINGITIS 85 

wall of the tube and mixed with the fluid. In the case of 
the meningococcus a smooth emulsion is usually rapidly- 
produced. Many of the other organisms are much less 
readily emulsified. 
An emulsion must be free of clumps for proper agglutination 

tests. 
The quantity in each tube should be 1 cc. The tubes are then 
incubated at 55° for twelve to eighteen hours, with neces- 
sary precautions against evaporation. 
Controls. Each culture should be run in parallel with a normal 
horse serum control at 1:50. A known meningococcus 
culture should be run at a positive control with each set. 
VIII. Reading of Agglutinations. 

The tubes which have been clarified are then shaken gently 
when the clumps can be clearly detected by the naked eye or 
hand lens. 
The organisms which are agglutinated by the polyvalent serum 

dilutions at 1 : 100 are to be regarded as meningococci. 
Organisms which agglutinate in both polyvalent and normal 

horse sera are to be thrown out. 
A slight opalescence in the supernatant fluid due to contaminating 
organisms, if there is otherwise distinct evidence of alggutina- 
tion, need not lead to the discard of the culture as negative. 
IX. Typing. 

The meningococcus isolated by agglutination with polyvalent 
serum should be typed as soon as possible. If this procedure 
cannot be carried out on the spot, the cultures, or heated 
suspensions of the cultures in saline with 0.5 per cent phenol, 
should be sent to the nearest Department Laboratory. 
XI. Typing of Organisms. 

Organisms recovered from spinal fluid or blood should be typed 
and compared with the organism isolated from the patient's 
nasopharynx. 
Inagglutinate strains are sometimes encountered. To establish 
further the nature of these organisms they should be grown 
on dextrose, maltose, and saccharose serum-litmus-agar. 
XII. Indications for Culturing. 

On the appearance of a case of cerebro-spinal fever, all contacts 
should be cultured for the detection of carriers as soon as 
possible. By contact is meant those intimately associated 
with the patient — that is, all those in the same tent or squad 
room with him, as well as his close associates at mess or 
elsewhere. 
Experience has shown the inadvisability of attempting to culture 
larger groups than this. 



8b CARRIERS IN INFECTIOUS DISEASES 

In military service, those who give positive cultures should be 
held in the detention camp until they have had three succes- 
sive negative cultures at five-day intervals. If a second case 
appears in the same company within a week of the first case, 
the whole organization should be swabbed. 
XIII. Disposal of Carriers. 

The ordinary carrier usually clears up in a week or two. 

Those who carry longer than this constitute the chronic carriers, 
and usually give large numbers of colonies or even pure 
cultures; these are probably the important cases from a 
public health point of view. 

Such carriers should not be recommended for furlough to their 
homes, nor discharged from the service without authority 
from the Surgeon General. 

TREATMENT 

Fortunately most carriers are temporary and the problem is 
relatively easy. They should be isolated and given the best of 
hygiene, especially out-of-door life. Correction of deformities 
including tonsillectomy may be necessary. 

Many antiseptics were tried during the war without definite 
success. In some instances the condition was made worse. 

Specific measures, vaccination or serum treatment, have no 
definite place in treating carriers. 

The handling of carriers in large numbers requires hospitaliza- 
tion and quarantine. The plan usually collapses. During the 
war carrier camps were maintained where regular work was done. 

Heist, Solis-Cohen, and Solis-Cohen: Jour. Immun., 1922, vii, 1. 
Medical Research Committee, London, Special Report Series, Nos. 2, 3, 

17, I and II. 
Blackfan, K D. : Medicine, 1922, i, 139. 
Nammack, C. H. : Med. Record, 1919, xcvi, 590. 



CHAPTER XI 
Pneumococcus Pneumonia 

Contrary to the usual historical sequence, carriers, of some sort 
at least, were discovered before cases in pneumococcus pneumonia. 
Both Sternberg and Pasteur, in 1890, demonstrated the presence 
of pathogenic micrococci in the saliva of healthy individuals 
before the possible relation of these organisms to pneumonia was 
established. Even when these organisms were recognized as 
pneumococci, there was little or no advance in epidemiology be- 
cause it was believed that pneumococci were homogeneous. Only 
within the last few years, since the recognition of types of pneu- 
mococci, has come the possibility of intelligent epidemiological 
and carrier work. It is now realized that the true carrier is a 
factor which cannot be disregarded. 

Before the differentiation of types, it was taught that pneumo- 
coccus pneumonia was largely autogenous and depended on a 
lowering of resistance. It is still true that this kind of pneumonia 
occurs, especially following influenza, but at least two-thirds of 
the cases of pure lobar pneumonia are caused, not by the kind of 
pneumococcus present in the mouths of normal persons, Type IV, 
but by Types I and II. These are the epidemic strains. They 
are not found ordinarily in the mouth except in convalescent or 
contact carriers. 

Type IV, or more exactly Group IV, occurs in 20 to 50 per cent 
of normal mouths. It produces about one-fifth of the total num- 
ber of cases, especially the secondary ones. It really stands for a 
collection of types which cannot be recognized and handled as such. 
Hence, Group IV carriers do not figure in the program. Type III 
and atypical Type II pneumococci stand between Group IV and 
Type I and Type II pneumococci. They are definite types but also 
occur normally in the mouth. The Type I and Type II carriers are 
the only ones which have a definite place in carrier work at present. 
The subject is a difficult one technically and the recent prevalence 
of influenza has confused the situation by the increase of other 

87 



88 CARRIERS IN INFECTIOUS DISEASES 

kinds of pneumonia. However, there is no doubt that the 
pneumococcus Type I and II are primary causes of disease (Cecil 
and Blake) and that the carrier relations prevail. In view of the 
technical difficulties of typing and of our known lack of control, 
the radical handling of the pneumonia problem by the carrier 
method is out of the question. Tests of virulence and suscepti- 
bility are also not yet available as practical measures. Something, 
however, can be done with convalescent carriers and immediate 
contact type carriers. The general situation must be handled 
by general hygienic measures, by isolation of cases and carriers 
and by specific vaccination. 

Convalescent carriers of Type I and II pneumococcus are defi- 
nitely known, as about 40 per cent of Type I and II convalescents 
have the type organism in their saliva. These are usually tem- 
porary, existing about a month, but may last longer. Contact 
carriers are also well recognized, having been found in over 10 
per cent of the Rockefeller Hospital series. They are also tem- 
porary, lasting about a month. The writer made a study of 
pneumonia in a large camp in 1916 and found evidences of squad, 
company and regimental type epidemics. Fifteen per cent of 
tent contacts of Type I cases were found to be temporary, contact 
carriers. No incubationary carriers were detected. 

PATHOLOGY 

No special carrier lesion is recognized for pneumococci. As 
most carriers are temporary it is probable that no special lesion 
exists. The pneumococci, apparently, live for a short time on 
the mucous membrane of the mouth like the more saphrophytic 
types. The tonsil, of course, is a favourable soil, but type carrier 
foci have not been definitely located there. There may be semi- 
chronic lesions in the lungs or bronchi, but they have not been 
identified. 

DIAGNOSIS 

The history of a recent attack of pneumonia or of contact with 
the disease raises the possibility, but the type of the previous attack 
or contact is often unknown. Bacteriological diagnosis must be 
depended on; serological reactions are not definite enough. 



PNEUMOCOCCTJS PNEUMONIA 89 

The technique is more difficult than in a case as the organisms 
are fewer and more mixed with others. A faucial swab or saliva 
can be plated on blood agar and suspected colonies fished to glu- 
cose broth for tests, but it is better to use the mouse method by 
injecting 0.5 cc. of mixed saliva into the peritoneum. Sometimes 
the peritoneal exudate can be used directly for typing as in cases, 
but often it is too much contaminated and cultures of heart blood 
or subcultures of peritoneal exudate must be made. The usual 
staining, agglutination and bile solubility tests must be made and 
sometimes be supplemented by cultural reactions. Occasionally 
two types may be found, as I and IV. Usually only one sapro- 
phytic type is present in the mouth. 

TREATMENT 

Cases should be isolated as far as possible and contact should 
be limited. Convalescent type carriers should be kept isolated 
for a reasonable time or until two or three negative cultures are 
obtained. Contact carriers should be warned of possible danger 
to themselves and others. They should be kept in good condition 
and avoid contaminating others. Usually they clear up in a 
short time. On analogy the nose and throat should be looked 
after for local predisposing lesions. No data are available on the 
results of the use of antiseptics. 

Laboratory facilities usually are too limited for any extensive 
general carrier work, but they should be used for this purpose as 
far as possible. 

Avery, O. T., Chickering, H. T., Cole, R., and Dochez, A. R.M: Mono- 
graphs of the Rockefeller Institute, No. 7, 1917. Acute Lobar 
Pneumonia. Prevention and Serum Treatment. 

Blake, F. G., and Cecil, R. L. : Studies on Experimental Pneumonia. 
Jour. Exp. Med., 1920. 

Nichols, H. J.: N. Y. Med. Jour., 1917, August 4; Met. Surg., 1917. 

Sailer, Hall, Wilson and McCoy: Arch. Int. Med., 1919, xxiv, 600. 



CHAPTER XII 
Streptococcus Infections 

Historically, the best known carriers of streptococci were the 
surgeons and students of the premicrobic period, who after treating 
cases of puerperal fever or making post mortem examinations, 
infected puerperal women by local examination. These were 
mechanical contact carriers who do not belong to the present age. 

The most important streptococcus carriers of today are those 
involved in the streptococcus diseases of the respiratory tract, 
such as tonsillitis, pharyngitis, rhinitis, sinusitis, otitis media, 
mastoiditis, bronchitis, pneumonia and empyema. The experi- 
ences of the war and of the influenza pandemic emphasized the 
seriousness of this group of diseases and much work has been done 
especially on the carrier relationships of streptococcus hemolyticus. 
It has been established that carriers exist and play a part in the 
spread of the organisms. Methods of treatment are also effective. 
The part played by carriers in the production of the disease is not 
so clear. The principal drawback is that we have no ready means 
of picking out true carriers from among possible and pseudo car- 
riers. The large scale on which any measures must be carried out 
is also a complication. Finally there is uncertainty as to the 
primary or secondary importance of the streptococci. Hence, the 
role of carriers is still obscure. Radical control by carrier meas- 
ures is not possible but the indications are to push the carrier 
program as far as conditions permit. 

There are of course other streptococci than the hemolytic types 
in the respiratory tract and in some cases the differentiation of 
feeble hemolyzers is not simple. Among individuals infected 
with these other streptococci, possible carriers exist. If the cur- 
rent views of the etiology of endocarditis and other forms of focal 
infection are correct, undoubtedly some virulent strains of strep- 
tococcus viridans are carried by certain individuals. At present, 
however, these true carriers cannot be picked out and attention 
must be confined to carriers of hemolytic streptococci. 

90 



STREPTOCOCCUS INFECTIONS 91 

Some workers claim that by repeated cultures hemolytic strep- 
tococci can be found in 100 per cent of throats. It is certainly 
true that a single culture gives no adequate picture of the ultimate 
bacterial flora of the throat, and that successive cultures increase 
the percentage of positive findings. The conclusion should not 
be drawn, however, that all hemolytic streptococci found in the 
throat are normal inhabitants. All the evidence points to the 
probability that there are different groups of streptococci and 
that there are true carriers. During the war surveys showed that 
recruits freshly arrived, especially from rural districts, had a 
relatively small percentage of positive findings, about 5 per cent, 
which soon increased to equal the high rates of those who had been 
longer in crowded camps, 50 to 80 per cent. These surveys were 
mostly made on single cultures and more thorough work might 
have raised the percentage, but could hardly have obliterated the 
striking difference. The number of carriers usually detected by 
ordinary examination is 10 to 20 per cent. 

In considering the question of groups of streptococci, it is 
fairly well settled that there is a distinct scarlet fever strepto- 
coccus. This differentiation has been made on immune reactions 
and confirmed by several different workers and is so clear cut 
that the question of the streptococcal origin of scarlet fever is 
again open. The further grouping of hemolytic streptococci is 
not so definite. Some workers (Dochez and Avery) have made 
four groups on immunity reactions, while another worker (Gordon) 
has made only one. The sugar reactions in all the groups are 
generally the same (Holman), but there is a distinct group of 
mannite fermenters (streptococcus infrequens). Virulence tests 
might be of great value but it is difficult to standardize a test and 
virulence falls off rapidly on subculture. Havens and Taylor 
have recently done some work in this line. They injected into 
the peritoneum of a mouse, one-fifth of a twenty-four-hour 
growth of the first blood-agar-slant-transfer from the original 
blood agar plate. Death in twenty-four hours was taken as the 
standard of virulence. They found that only 10 to 15 per cent 
of strains from carriers were virulent while of strains from acute 
respiratory cases about 85 per cent were virulent. Virulence 
diminishes rapidly after an attack of tonsillitis, for example, but, 



92 CARRIERS IN INFECTIOUS DISEASES 

as the authors point out, it is impossible to assume that these 
organisms might not be or become virulent for a non-immune. 

Group carriers. The only way to approach the subject is to 
regard carriers of streptococcus pyogenes and streptococcus in- 
frequens (Holman) as possible carriers. Walker and Norton have 
shown that the infrequens group can be studied as a unit clinically 
and epidemiologically. As virulence and susceptibility are better 
understood, it will be possible to concentrate on the true carriers. 
The carrier is probably dangerous to himself as well as to others. 
In other words, relapsing carriers exist who suffer clinically when 
their immunity decreases. 

PATHOLOGY 

The most definite carrier lesion is found in the tonsil. Other 
foci may exist in the adenoids, turbinates and gums but the tonsil 
is the richest and most persistent source of the organisms. The 
lesion consists of an actual infection of the crypt wall. The 
epithelial lining is disintegrated and infiltrated with polynuclear 
leucocytes (fig. 11). Streptococci are also found in the crypt con- 
tents, especially in the actinomyces-like granules (Davis). 

The typical lesion is found in chronic convalescent carriers. 
Hypertrophied tonsils are most apt to be positive. Eighty per 
cent of such removed tonsils give a positive culture. In contact 
carriers the streptococci probably also lodge in the tonsil. It is 
impossible to state the exact pathogenesis in these carriers. The 
carrier is probably temporarily immune to his own organism, but 
repeated attacks of tonsillitis are of course the rule. 

DIAGNOSIS 

The presence of hypertrophied tonsils in young individuals is 
suggestive. Persons with clean tonsillectomies are rarely carriers 
or if so, carry few organisms. The actual diagnosis is bacterio- 
logical. The specimen should consist of crypt contents and is 
obtained by pressing the ordinary throat swab on the tonsil or 
going into the crypts with a loop. Occasionally the lesion is uni- 
lateral. Well spread smears are made on 5 per cent blood agar 
plates and after twenty-four hours incubation, hemolyzing colonies 
are examined by staining for Gram positive cocci in chains. The 



STREPTOCOCCUS INFECTIONS 93 

hemolytic influenza bacillus and hemolytic staphylococcus must 
be ruled out. A presumptive diagnosis can often be made on 
clear cut hemolysis in the original plate and speed- is an object 
when cases are being held for the results of cultures. Frequently 




Fig. 11. Drawing of Section of Tonsil of a Streptococcus haemolyticus 

Carrier. X 1000 

Streptococci are shown in the disintegrated epithelial covering 

the hemolysis is not clear cut. The colony must be subcultured 
into broth and a hemolysis test made with 0.5 cc. of twenty-four 
hour broth culture and 0.5 cc. of a 5 per cent suspension of red 
cells. Even with this test some results are partial and doubtful. 
Such organisms are usually regarded as non-hemolytic. Further 



94 CARRIERS IN INFECTIOUS DISEASES 

subdivision is made by sugar reactions, on lactose, mannite and 
salicin. Inulin and bile solubility tests are used to exclude 
pneumococci. Immunological classification of carrier strains is 
not on a practical basis. Virulence tests are also not standardized. 

TREATMENT 

As in diphtheria carriers, many attempts have been made to 
cure streptococcus carriers by the local application of antiseptics. 
The results have been disappointing. If the streptococci were 
simply growing on the surface of the crypt walls and if the crypts 
were all accessible, this line of treatment would be more effective. 
But the streptococci are often actually in the wall of the crypts 
and the crypts have underground connections which cannot be 
reached except by dissection. The most effective antiseptic in 
securing negative cultures is 25 per cent silver nitrate, but strepto- 
cocci can still be cultivated from the depths of the crypts after 
soaking an excised tonsil in a 25 per cent silver nitrate solution. 

The surest method of treating carriers is tonsillectomy. Most 
cases clear up immediately after the operation. In some instances 
a few streptococci can be found after clean tonsillectomies, but 
the danger of transmission is of course greatly reduced with the 
number of organisms. The operation should not be done until a 
month or two after an acute attack, in order to avoid systemic 
infection. The operation must also be a complete one as a small 
tag of tissue may be a carrier focus. 

X-ray and radium treatment have been proposed as a substitute 
for tonsillectomy and in selected cases, in which there is a con- 
traindication to operation, should be tried. Undoubtedly some 
tonsils contract considerably under this treatment and the num- 
ber of organisms become smaller. But the large hypertrophied 
tonsils are less suitable than the boggy ones for X-ray treatment. 
Several treatments are also required and while there may be 
clinical improvement, in many instances the streptococci persist. 
This result is of course a failure from the social point of view. 

Probably only in isolated instances will an operation be done 
simply for the carrier state. This state, however, is an additional 
argument for the operation when coupled with clinical indications. 




STREPTOCOCCUS INFECTIONS 95 

The following recommendations were made at a symposium on 
this subject in 1919: 

I. Our knowledge of hemolytic streptococcus carriers is so in- 
complete that every effort should be made to answer the following 
questions : 

a. Are streptococci found in carriers all of equal importance, 
or are there different groups which differ in clinical significance? 

b. Is the chronic carrier dangerous to himself? 

c. Is the chronic carrier dangerous to others, or is the disease 
spread chiefly by cases or by case contact carriers? 

II. In the absence of knowledge on these points, no final pro- 
gram for handling the problem can be stated, but a tentative 
program should be adopted which in case of doubt should err on 
the safe side. 

III. When no streptococcus disease is present and in off seasons. 

A. For soldiers in hospital. Incoming patients with throat 
infections should be cultured for hemolytic streptococci. Any 
positive case with diseased tonsils should have a tonsillectomy. 
Clean and infected measles wards should be maintained for prac- 
tice in ward technic. 

B. For soldiers in barracks. Clinical and cultural surveys 
should be made for the detection of chronic streptococcus infec- 
tions such as tonsillitis and otitis media, which when discovered 
should be treated to remove possible foci of future epidemics. 

IV. In the presence of streptococcus complications and during 
the streptococcus season. 

A. In the hospital. 

1. No carriers among attendants should be allowed in surgical 
wards or in wards with respiratory diseases. 

2. A streptococcus isolation ward should be established to 
handle special cases. 

3. Positive and negative measles, pneumonia and nose and 
throat wards should be maintained with strict technic. 

4. All admissions should be isolated until distributed to wards. 

5. Throat cultures for hemolytic streptococci should be made 
on all admissions with respiratory diseases for record. 

B. In barracks. 

1. Recruits should be held for observation and cultured. Posi- 
tive cases should be separated from negative as far as possible. 



96 CARRIERS IN INFECTIOUS DISEASES 

2. Clinical and cultural surveys should be made to pick out 
cases of tonsillitis, otitis media, sore throat which should be sent 
to hospital. 

V. In the absence of exact knowledge and with due regard to 
military necessity, no attempt to isolate all streptococcus carriers 
is advocated at present. 

Havens, L. C, and Taylor, M. L.: Am. Jour. Hyg., 1921, i, 192. 

Bryan, J. H., Nichols, H. J., Avery, O. T., Dochez, A. R., and Lance- 
field, R. C, Blake, F. G., and Russell, F. F. : Symposium 
on Streptococcus Hemolyticus Carriers. Annals of Otolog3% 
Rhinology & Laryngology, June, 1919. 

Methods for Isolation and Identification of Streptococcus Hemolyticus 
adopted by the Medical Department of the U. S. Army. 

Walker, J. E.: Jour. Exp. Med., 1920, xxvii, 618. 

Sharp, W. B., Norton, J. F., and Gordon, J. E. : Jour. Inf. Dis., 1922, 
xxx, 372. 

Kelbert, Ellis: Jour. Med. Res., 1920, xli, 387. 

Levy, R. L., and Alexander, H. L. : Jour. Amer. Med. Assoc, 1918, lxx, 
1146. 

Nichols, H. J., and Bryan, J. H. : Jour. Amer. Med. Assoc, 1918, lxxi, 
1813. 



CHAPTER XIII 
Other Respiratory Infections 

By analogy the carrier aspects of the large group of diseases 
known as colds, influenza, etc., are undoubtedly important, but 
little practical headway can be made along carrier lines on account 
of the uncertainty as to the etiology of these diseases. Many 
different organisms have been put forward as causes, but none is 
fully accepted as a primary factor. The possibility of a primary 
filterable virus must be disposed of before any advance is made. 
As MetchnikofI says, this possibility is a "sort of ghost preventing 
all definite conclusions in problems connected with the absence 
or presence of microbes." On grounds of epidemiology and anal- 
ogy there are probably incubationary carriers, convalescent 
carriers, either temporary or chronic, and contact carriers. But 
as long as the parasite is unknown, nothing can be done along 
carrier lines except to isolate cases early and continue the isolation 
for a reasonable time. There is no better illustration in medicine 
for the necessity of scientific knowledge as a basis for practical 
work. Our good intentions and organizations are helpless with- 
out it. 

INFLUENZA 

The influenza bacillus is the principal storm center in this dis- 
cussion. It has been found in 100 per cent of cases of influenza 
by combined cultures and animal inoculations. It has also been 
found in about 30 per cent of convalescents. On the other hand, 
it has been found in about 20 per cent of normal non-contact 
individuals. The value of any set of statistics can not be deter- 
mined until there is an answer to the following questions: Is any 
form of the influenza bacillus the primary cause of influenza? 
Are there groups of the organism, epidemic and saphrophytic? 
What part is played by changes in virulence? Until we have 
more definite knowledge on these points, no practical carrier work 
can be done. 

97 



y» CARRIERS IN INFECTIOUS DISEASES 

Irrespective of its relationship to influenza, the influenza bacillus 
is recognized as a pathogene, especially in meningitis in children. 
There is some evidence of the existence of a special meningitis 
group of organisms (Rivers). The hemolytic influenza bacillus 
is usually regarded as non-pathogenic. 

Pathology 

The sinuses, especially the sphenoids, are foci for the influenza 
bacillus (Hopkins and Robertson) . At autopsy a purulent exu- 
date with a pure culture is frequently found. The working out 
of the significance of the lesions depends on the outcome of the 
work on the problem of etiology. 

Diagnosis 

The diagnosis is a purely bacteriological one. The more speci- 
mens from different parts of the respiratory tract examined, the 
higher are the positive results. Usual throat swabs are inocu- 
lated on chocolate agar and colonies made up of Gram negative 
bacilli are transferred to blood agar and plain agar. The results 
of these cultures indicate whether the organism is hemoglobino- 
philic or hemolytic. Further test may be made for indol produc- 
tion (Jordan) which separates 40 to 50 per cent of influenza bacilli 
from Koch- Weeks bacilli. Toxicity tests and grouping at pres- 
ent are not available. 

Treatment 

In view of the uncertainties mentioned above, no radical carrier 
procedures are justified. Cases should be confined to bed in 
isolation for a reasonable time. 



This condition shares with others in uncertainties of carrier 
work. It is disabling and at times is undoubtedly epidemic. 
During the war the disease was quite prevalent in the form of 
" trench mouth." In attempting to handle the situation along 
rational lines we are again confronted with a wilderness of con- 
fusion. The organisms of Vincent's angina may be accepted as 
causal but they occur, at least in small numbers, in normal mouths 



OTHER RESPIRATORY INFECTIONS 99 

in a very high percentage of individuals. They are practically 
normal inhabitants. On the other hand, apparently some strains 
are virulent and produce ulcers and spread to others. How are 
the two organisms related to each other and to the disease? Are 
they primary or secondary causes? If primary, how can the 
epidemic strains be identified? There is no adequate answer at 
present to these crucial questions. Hence no scientific basis 
exists for carrier work. 

During the war some enthusiastic medical officers, especially 
dental officers, tried to enforce the carrier program by isolating 
all cases until negative release examinations were obtained. Con- 
tacts were quarantined on the mere presence of a few fusiform 
bacilli and spirochetes in smears. These measures threatened to 
entirely tie up the activities of one camp and were ordered dis- 
continued on the basis that our knowledge does not justify such 
a radical program. The situation must be handled by treatment, 
hygiene and sanitation rather than carrier work at present. 

TUBERCULOSIS 

The term carrier is sometimes used in tuberculosis to indicate 
an apparently healthy person who discharges tubercle bacilli. 
Such true convalescent carriers may exist who have a general 
immunity with a small unhealed lesion somewhere in the body. 
But, in general, such individuals should be considered as mild or 
chronic cases. In view of the nature of the disease and of its mode 
of spread, more good will be done to the individual and to the 
group by emphasizing cases rather than carriers. 

On the other hand, if the term is accepted, there are a large 
number of true relapsing carriers. As infection apparently occurs 
in childhood and clinical cases later in life are due to an autogenous 
spread from a chronic glandular focus, we may say that relapsing 
carriers are of the greatest importance in this disease. The danger 
is primarily individual and secondarily social. One organ be- 
comes the unit and the individual represents a group of organs. 
According to this analysis, the relapsing carrier comes under the 
definition of a carrier, as an individual who harbors and transmits 
a pathogenic parasite, only as the parasite is transmitted from 
one organ to another. This extension of the carrier conception is 
perhaps undesirable; but, even from the practical point of view, 



100 CARRIEKS IN INFECTIOUS DISEASES 

a consideration of the importance, pathology, diagnosis and 
treatment of relapsing carriers as seen in latent and focal infections 
is instructive. 

DISEASES OF UNKNOWN ETIOLOGY OR DUE TO FILTERABLE 

VIRUSES 

There is a formidable list of so-called respiratory diseases in 
which little practical carrier work can be done as the cause is 
unknown or, if known, requires such a special technique for identi- 
fication that it cannot be handled clinically or in a public health 
sense. This list includes measles, scarlet fever, mumps, smallpox, 
chicken pox, poliomyelitis, encephalitis and possibly influenza and 
colds (Foster). 

Work on poliomyelitis has been most instructive in this group 
and gives a rational basis for at least some carrier measures. The 
possibility of carrier transmission was opened up by epidemiolog- 
ical studies before experimental confirmation occurred. After 
the virus was identified, it has been shown by animal inoculation 
(1) that incubationary carriers exist (Taylor and Amoss); (2) that 
convalescent carriers exist, occasionally lasting seven months; 
(3) that contact carriers occur which probably out-number cases 
and play as important a role as a meningococcus carrier; (4) that 
the tonsils are foci in carriers. 

Considering the experimental difficulties involved in this work, 
it must be clear that even the few observations on which these 
statements depend have thrown much light on the problems of 
prevention of this disease and the entire group. While it is 
usually impossible to do individual carrier work at present on 
account of the lack of laboratory facilities, some general rules can 
be laid down. Cases should be isolated at the earliest possible 
moment. Logically the same rule should apply to any indefinite 
sickness in childhood, but is usually out of the question. Conva- 
lescents should also be isolated for about three weeks. Contacts, 
if they occur, should be under suspicion. The tonsils are again 
shown to be a menace and the hygiene of the nose and throat is 
emphasized. 

Vaughan, V. C: Epidemiology and Public Health. 1922, vol. I. C. A., 

Mosby & Company, St. Louis. 
Opie, Blake, Small and Rivers: Epidemic Respiratory Disease. 1921, 

C. V. Mosby and Company, St. Louis. 



CHAPTER XIV 
Blood Diseases 

This group might also be called the insect transmission group 
as the parasites live largely in the blood vessels and exit is usually 
provided only by puncture of a blood vessel. 

MALARIA 

Carriers play a well known part in the continued existence of 
malaria. As in amoebiasis, there are special forms of the parasite, 
called gametes, whose function it is to perpetuate the life of the 
parasite in the insect host. The vegetative forms which produce 
the symptoms are not infective for the mosquito, but in about 
50 per cent of cases, gametes are found and convalescent or re- 
lapsing carriers result. The gametes are more numerous in the 
chronic than in the acute stages of the infection. Hence all the 
circumstances are favorable for the infection of the mosquito by 
the carrier. 

In malarious regions gametes are found in the blood of about 
10 per cent of apparently healthy adults. In children the per- 
centage may be much higher. Strictly speaking, all carriers in 
malaria belong to the convalescent carrier group either as chronic 
convalescent or relapsing carriers. An infection of the red cells 
by the vegetative forms is necessary before the sexual stages can 
develop. Hence, the true contact carrier does not exist. Prac- 
tically speaking, however, such carriers do exist in the sense that 
they have never been conscious of their original infection. 

Pathology 

Carriers in malaria are particularly instructive from the point 
of view of immunity. There is a true infection but a balanced 
parasitism which is apparently reached by an antitoxic without 
an anti-parasitical immunity. A special focus exists in the 
capillaries of the spleen, liver and brain. The balance is delicate 
and toxic symptoms or frank relapse may occur. 

101 



102 CARRIERS IN INFECTIOUS DISEASES 

Diagnosis 

Previous residence in malarial regions is suggestive. Clinical 
examination may show an enlargement of the spleen. In the 
laboratory examination an increase of mononuclear leucocytes is 
suggestive. The actual finding of the parasite is more difficult 
than in cases, as the parasites are fewer and the gamete must be 
identified. In aestivo-autumnal infections, however, the gamete 
has a characteristic crescent shape which is distinctive. It has 
been estimated (Darling) that a certain percentage of gametes 
per mm. of blood is necessary for infection of the mosquito and, 
therefore, to constitute a carrier. Usually an ordinary blood film 
is made and stained by a polychrome method. The thick film 
method is valuable in experienced hands. Cultural methods 
(Bass) are difficult technically and reveal only the vegetative 
forms. Various drugs have been suggested to bring the parasites 
into the peripheral circulation such as ergot and adrenalin. Ultra 
violet light has also been used to produce relapses. 

Treatment 

The prompt treatment of an acute case with quinine prevents 
the development of gametes and hence prevents carriers. After 
the infection is established the treatment of carriers must be more 
prolonged, as the gametes are not affected by quinine. The 
formation of new gametes can be prevented however, and the old 
forms gradually disappear from the blood. Intravenous therapy 
is no more effective than alimentary. In carriers who do not 
tolerate quinine, arsphenamine should be used. 

OTHER DISEASES OF THE BLOOD 

The most important other infectious diseases of the blood are 
relapsing fever, yellow fever, trypanosomiasis, filariasis, bubonic 
plague and typhus. Human carriers are not known in yellow fever, 
plague or typhus. If they occur, the parasite probably leaves the 
body by some other avenue than the puncture of a blood vessel by 
an insect. 

Trypanosomiasis is so progressive and fatal a disease that true 
carriers do not occur in the human host. In the animal host, 
carriers are considered in a later section. 



BLOOD DISEASES 103 

Filariasis is a true carrier disease in the sense that the infected 
individual often shows no evidences of disease. The commonest 
variety of infection is due to Filaria Bancrofti. This disease is of 
most importance among native races in the tropics, but there is 
a focus in Charleston, South Carolina, and white men are occa- 
sionally infected in the tropics. Probably the infection occurs 
principally in early life. The distribution is often sharply local- 
ized. Carriers of microfilaria may run from 5 to 20 per cent in 
an endemic area as in certain islands in the Philippines, while 
in other islands the rate is much low T er. 

Pathology 

The mother worm is so situated in the lymphatics that no 
symptoms arise. Sometimes there are internal evidences of 
disease with none externally. 

Diagnosis 

Residence in an endemic area is suggestive. Examination of 
night blood shows the characteristic periodicity of parasites in the 
peripheral circulation. The parasite can also be found by exami- 
nation of a large amount of day blood. 

Treatment 

No active treatment is effective at present. Carriers should 
be protected from mosquito bites to prevent spread. They can 
be disregarded otherwise. 

SKIN DISEASES 

The skin is of course infected by various bacteria, fungi, blas- 
tomycetes, spirochetes, protozoa and metazoa and definite carrier 
aspects of some of these infections occur. It is not considered 
worth while, however, to enlarge on this subject in this manual at 
present. The lesions are usually so noticeable and so accessible 
for local treatment that possible carrier lesions are usually regarded 
as mild or chronic cases. 



CHAPTER XV 

Sexual Diseases 

1. syphilis 

As in tuberculosis, it may be questioned whether it is correct 
to speak of carriers in syphilis rather than of latent cases. The 
infection is so apt to be slowly progressive that this criticism has 
some point. But, unlike tuberculosis, syphilis is usually spread 
by a form of contact which has special carrier aspects. It also 
has such a direct although insidious effect on the welfare of the 
race that an exception should be made, if necessary, to emphasize 
the social menace of the situation. The prospective bridegroom, 
infected but apparently healthy, is really carrying spirochetes 
which will disable his wife and blight his offspring. It is splitting 
hairs at the expense of public health not to recognize that the 
apparently well syphilitic is a great danger in the organized social 
relations of marriage. For practical purposes, therefore, cases of 
latent syphilitic infection, especially males, may be considered 
carriers. They have all the characteristics of apparent health 
combined with the most malign possibilities for harm that other 
carriers present. The female infects only through an open active 
lesion or occasionally as a mechanical carrier. 

The number of latent male cases is somewhat problematical as 
it depends on the whole number of cases which is variously esti- 
mated by different workers. If we assume, as we can on good 
grounds, that 10 per cent of adult males at any one time have 
syphilis and that 50 per cent of these are in a latent stage, then 
there would be over 1,000,000 such carriers in the United States 
at present. They can be classed as chronic convalescent carriers 
as they have recovered from the acute generalized stage of the 
disease and have reached the stage of localization, or they can be 
considered as relapsing carriers. 

104 



SEXUAL DISEASES 105 

Pathology 

The carrier lesion is in the testicle in the great majority of car- 
riers. There are many other foci of spirochetes in the blood 
vessel walls of other organs and in the nervous system, but these 
have no natural outlet. The lesions have been most carefully 
studied by Warthin by the combined method of ordinary histology 
and of sections stained for the organism. They consist of small, 
often microscopic, collections of lymphocytes among which are 
nests of spirochetes. In the testicles these foci communicate with 
the tubules and the organisms are discharged with the semen. 

The seriousness of the situation consists in the fact that the 
spirochetes are genito tropic. Experimental work has shown that 
the testicles are the most favorable place for their growth and that 
they lodge there by preference. Their distribution elsewhere in 
the body may be determined partly by chance, but they will 
certainly lodge in the testicle in the great majority of cases. 
The carrier is temporarily immune to the toxic effects of the 
parasite, but not locally immune to the parasite itself. A balanced 
parasitism is reached as in other carriers. 

Diagnosis 

Illness of the sexual partner, miscarriage and stillbirths are 
suggestive. A truthful personal history with clinical examination 
may be almost conclusive, as the presence of a primary scar with 
adenopathy and the history of previous treatment is very sus- 
picious. Very often, however, the carrier is truly unaware of his 
condition. The original attack has been mild and unnoticed. 
For exact diagnosis, a confirmed completely positive Wassermann 
reaction, done by a competent serologist and in the absence of 
certain rare diseases, is conclusive evidence of syphilis. This 
test, taken with the results of clinical examination, are usually 
convincing. Weak reactions and indefinite clinical signs of course 
occur and make it necessary to balance probabilities. A provoca- 
tive Wassermann is sometimes valuable. Examination of the 
spinal fluid is justified in doubtful cases as nervous system involve- 
ment is probably second to that of the generative organs. 



106 CARRIERS IN INFECTIOUS DISEASES 

The diagnosis by the demonstration of the spirochetes in the 
seminal fluid has been made both by direct examination and by 
animal inoculation. The specimen can be obtained by use of a 
condom or by massage of seminal vesicles. Examination by the 
dark field microscope or by injection into rabbits' testicles have 
given positive results in apparently well individuals who were 
candidates for marriage. These procedures, however, belong more 
to research than to clinical medicine. The virulence of the para- 
site apparently decreases somewhat as the disease progresses, but 
both experimental inoculation and clinical experience show that 
the virulence remains for years high enough to infect. 

Treatment 

This is the usual one for the disease — the chronic combined 
treatment with arsphenamine and mercury. In general the 
author believes that optimism as to results is justified. Standards 
of cure are not entirely agreed upon; but a carrier should not be 
considered safe for marriage until he has had definite treatment 
and a negative serological and clinical year has elapsed with no 
treatment. Mechanical protection against direct contact can of 
course be used. 

2. GONORRHOEA 

True carriers exist in gonorrhoea, both in males and in females, 
and are responsible for a good share of the trouble caused by the 
gonococcus. The principal bad effects are blindness in children, 
sterility and chronic ill health in women, stricture, prostatitis and 
arthritis inmen. The line between a chronic case and a carrier can be 
drawn by giving sufficient attention to history and examination. 
Most carriers are of the convalescent type. The percentage of 
complete cures is not very large. The pure contact carrier may 
apparently occur in the prostitute. She may be a primary or 
secondary contact carrier and may transmit the organisms 
mechanically from a case or carrier to the new case. 

Pathology 

Small inflammatory or ulcerative lesions persist in the urethra, 
prostate, seminal vesicles and epididymus or in the cervix, urethra 



SEXUAL DISEASES 107 

and Bartholin glands. They are usually quiescent, but may 
become active after sexual intercourse, alcoholism and menstrua- 
tion. The true carrier lesion is one in which there is a local lesion 
but a general immunity. 

Diagnosis 

Social circumstances and history may suggest the examination. 
Local examination may reveal a focus. The final diagnosis is 
either bacteriological or serological, but in either case difficulties 
may be met. The specimen should be obtained as directly from 
the lesion as possible. Definite Gram negative intracellular cocci 
in discharge from the genital organs is practically diagnostic. In 
some cases the organisms can be isolated by cultures and confirmed 
by cultural and serological reactions. Too often a few cocci may 
be found extracellularly which cannot be isolated in pure culture. 
The unsatisfactory nature of this situation was recognized by the 
Inter-Departmental Social Hygiene Board and work along these 
lines was encouraged. A precipitin test was devised which con- 
sisted in the testing of an autolyzed exudate against a known 
serum. It gives clear cut results at times, but is not entirely 
specific. The complement fixation test is also useful if positive, 
but is often negative in known carriers. Altogether the detection 
of the carrier is not very satisfactory, but something can be done. 
Regional location of foci is necessary after the organism has been 
found or serological evidence of its presence has been obtained. 

Treatment 

The usual local antiseptic treatment is indicated. New mer- 
cury compounds (Young) have more than ordinary promise. 
Specific treatment is uncertain but has followers. Non-specific 
treatment also has its advocates. Local treatment after identi- 
fication of foci is most helpful. 

Marriage should not be allowed until the possibility of the 
carrier state has been ruled out. 



108 CARRIEKS IN INFECTIOUS DISEASES 

3. OTHER VENEREAL DISEASES 

Carriers of Ducrey bacilli are not definitely known. If we 
admit a fourth venereal disease in the fusospirillary infection, the 
carrier relationships of this infection are unknown, but probably 
resemble those in Vincent's angina. 

Vedder, E. B. : Syphilis and Public Health, 1918, Lea and Febiger, Phila- 
delphia and New York. 

Nichols, H. J.: Jour. Amer. Med. Assoc, 1914, lxii, 1525; lxjii, 466. 

Young, H. H., White, E. C, and Swartz, E. O. : Jour. Amer. Med. Assoc, 
1919, lxxiii, 1483. 



PART III 
SUMMARY 



CHAPTER XVI 

The Relations of Phokology to Preventive Medicine 

1. the place of carrier work in preventive medicine 

Preventive medicine, as applied to the infectious diseases, has 
a many sided program which is daily producing results. This 
program may be outlined as follows : 

A. Prevention of the spread of parasites from the point of 
multiplication which is usually in the host. This procedure 
involves early treatment in the home or hospital, the disinfection 
of infectious discharges, isolation and quarantine. 

B. Prevention of the spread of parasites in the environment. 
This is one of the aims of sanitation and includes the disinfection 
of food, drink, air and the destruction of insects. 

C. The personal prevention of attacks by parasites, or personal 
hygiene. This field includes the increase of personal resistance 
and the avoidance of risks of infection. 

D. Specific immunity by vaccination or serum prophylaxis. 
Any one of these measures if logically and completely carried 

out would put an end to an infectious disease, but it would be day 
dreaming to imagine that any one or all of these measures can be 
completely carried out for all infections. However, by suitable 
selection of means for ends, many solid results are being obtained. 

Carriers come under consideration in each part of this program. 

A. The measures which have been so effective against case 
transmission are equally effective against carrier transmission. 
Some cure themselves under quarantine or observation, others 
can be cured by treatment. The relative amount of attention 
which should be paid to cases and carriers from this point of view 
has been considered under each disease. The program of course 
includes the diagnosis of carriers and this is one of the limitations 
of this method for carriers as it is for cases. To really diagnose 
and treat every case and carrier of an infectious disease, especially 
during an epidemic, would require an organization which would 

111 



112 CARRIERS IN INFECTIOUS DISEASES 

break down of its own weight. There would have to be a labora- 
tory at every corner and an inquisition in every home. A medical 
officer of a transport once estimated that if ideal ventilation was 
provided on all parts of the boat, all the power would be used up 
on fans and the boat would be standing still in the middle of the 
ocean. The same absurd conclusion would be reached by trying 
to enforce the carrier program to the bitter end. As was evident 
during the war, the work of detecting and handling carriers was 
often out of the question on account of the amount of work and 
the interference with the aim. Life must and will go on spite of 
infections. On the other hand, a more modest attempt is often 
feasible and effective on a small scale. While, therefore, this 
method is logically and practically effective within limits, it alone 
cannot be counted on to prevent disease. 

B. Granting that other measures are necessary, sanitation 
accomplishes a great deal and must be directed against carriers 
as well as against cases. The relative amount of protection neces- 
sary against carriers cannot be accurately stated, because the 
dangers are unknown. A water supply must be unnecessarily 
chlorinated for many days of the year in order to be safe for the 
whole year. Sanitation undoubtedly cuts off many sources of 
infection from carriers in water, milk, food and air. The limita- 
tions of this method are its breakdown at critical lines due to 
accident or human weakness and to its failure to cover contact 
infection. We have at present no means of sterilizing respiratory 
droplets in the air of street cars or movies. 

C. Personal hygiene has advantages and limitations as applied 
to carriers. It usually consists of two parts, the maintenance of 
resistance and personal care to avoid infection. The maintenance 
of a clean nose and mouth is of advantage as it is a partial pro- 
tection from becoming a contact carrier. Care in personal habits 
is effective against carriers as against cases. There are limitations 
to this part of the program, however, as is shown in the recent 
development of "bacteriophobia." Some individuals, including 
even physicians, have become so particular about exposure that 
they have lost their value as social beings. The soldier cannot 
think of personal hygiene as applied to war injuries. There are, 
however, practical and reasonable applications which are of value. 



PHOROLOGY AND PREVENTIVE MEDICINE 113 

For the carrier himself personal hygiene means preventing the 
exposure of others to his own infection. 
The following is a summary of rules : 

a. For faecal and urinary carriers: 

(1) Deposit feces and urine only in places provided for such a 
purpose and not where they can knowingly infect a water supply. 

(2) Wash hands with soap and water after going to the toilet. 
Use individual paper or towel. 

(3) Wash hands before each meal. Use individual eating 
utensils. 

(4) Do not engage in food handling occupation. 

(5) Disinfect soiled underclothing in 5 per cent carbolic acid 
solution. 

(6) Do not use common bath tub; use sponge or shower bath. 

(7) Report to physician for periodic examination. 

b. For the respiratory carrier 

(1) Dispose of discharges from nose and throat in a safe way, 
in spittoon or handkerchiefs. Do not spit promiscuously. 

(2) Use personal eating utensils. 

(3) Wash hands when soiled with respiratory discharge. Use 
individual towel. 

(4) Avoid close contact in talking; avoid kissing. 

(5) Report to physician for treatment and regular examinations. 

c. For genito-urinary carriers 

(1) Avoid sexual intercourse, unless with protection. 

(2) Do not marry without permission of a physician. 

(3) Take regular treatment. 

(4) Have periodic examinations. 

d. For the blood carrier 

(1) Avoid bites of mosquitoes by screens and bed nets. 

(2) Kill mosquitoes found in room. 

(3) Follow lines of treatment. 

(4) Have periodic examinations. 

D. Vaccination. This is one of the best all around measures of 
preventive medicine as the chemistry of the body is made immune. 
This immunity is of course effective against carrier strains as well 
as case strains. Its limitations lie in the fact that there are many 
severe diseases against which no vaccination is available and the 



114 CARRIERS IN INFECTIOUS DISEASES 

fact that the immunity to smallpox and typhoid is relative and 
temporary. The immune person may also become a contact 
carrier, but this condition is usually temporary. 

The combination of all these methods is very effective and 
prompts the enthusiast to draw pictures of a disease free world. 
The place of carrier work in this program should neither be exag- 
gerated for its own sake nor minimized in favor of other measures. 
It should be given its proper value in the major project. 

2. THE METHOD OF CARRIER WORK 

1. The first and most obvious place to start carrier work is 
with the case. If a case can be diagnosed by demonstration of a 
parasite, a carrier can be detected by the same methods. The 
list of diseases in which release examinations can be made is small 
in comparison to the total number of diseases but large in com- 
parison to actual practise. Some few diseases, such as diphtheria, 
are covered by law or regulations, but others, as typhoid, are left 
to the practitioner's judgment. A great advance will be made in 
carrier work when release cultures are insisted on whenever pos- 
sible. Convalescence has several advantages for carrier work. 
There is usually plenty of time for careful examination. Early 
diagnosis is possible before any harm is done and treatment is 
easier, as it joins on to the treatment of the case. 

A single adequate examination after an infectious disease would be 
sufficient to dispose of the carrier question. For example, a single 
adequate examination of bile ducts after typhoid, or of the naso- 
pharynx after diphtheria or meningitis would in the great majority 
of cases be sufficient, but usually specimens and examinations are 
more or less inadequate. Several release examinations are there- 
fore wisely insisted on. The specimens should be taken, if neces- 
sary, by a "phorologist" who is interested in finding the parasite, 
rather than by a physician who may be chiefly interested in re- 
ceiving a negative laboratory report. 

2. The next logical step is to examine contacts. This examina- 
tion has a double object. On the one hand, it may be possible 
to pick up the carrier who has caused the case in question, or, on 
the other hand, it may be possible to diagnose other carriers who 
have been infected by the case. The extent to which this work 



PHOROLOGY AND PREVENTIVE MEDICINE 115 

should be carried must be determined by the indications and com- 
mon sense. The problem is fairly easy in a small group such as a 
family, but becomes more difficult in schools, offices and among 
troops. As laboratory facilities increase, this phase of the work 
tends to increase. As experience increases, we will be more able 
to give a more exact program. 

3. In addition to the case and the contacts there are several 
general measures which are practical and valuable. The first 
of these is the examination of special groups such as food handlers. 
If the amount of sickness due to ignorant and careless servants 
were accurately known, it would probably be a shock to most 
people. The worst conditions are usually found in the colored 
races. Public eating places as well as homes are subject to con- 
tamination in this way. These examinations should relate pri- 
marily to intestinal carriers, but milkmen should be examined for 
diphtheria carriers and possibly streptococcus carriers. 

4. Another practical line of carrier attack is in applicants for 
positions. They are usually subject to some examination and the 
common carrier conditions can gradually be included. As more 
exact methods are becoming available for the evaluation of the 
individual, it is being realized as never before that a real examina- 
tion should include the whole organism, mental and physical. 
If we go one step farther and view the individual as a social being, 
it is also indicated to determine whether he is a carrier. The 
actual examinations to be made should depend on previous sick- 
ness, the nature of the work and the prevailing diseases. Under 
varying conditions these examinations should include the follow- 
ing procedures: (1) A nose and throat swab could be made and 
blood serum tubes could be inoculated for growth of the diphtheria 
bacillus. (2) A tonsil swab could be made and the specimen 
examined on a blood agar plate for hemolytic streptococci. (3) 
A nasopharyngeal swab could be made and the material examined 
on laked blood agar plates for meningococci. (4) The saliva could 
be examined for pneumococci by the mouse method. (5) The 
feces and urine could be examined for typhoid group of bacilli. 
(6) The feces could be examined for the organisms of cholera and 
dysentery. (7) A blood film could be examined for malarial 
gametes or filaria. 



116 CARRIERS IN INFECTIOUS DISEASES 

5. A similar time and place for carrier work is at the regular 
physical examinations which are becoming more and more fre- 
quent. These examinations are usually made for the personal 
benefit of the individual but should be broadened to include the 
welfare of the group. The success of the work would depend 
naturally on the common sense and care with which it was planned. 

6. A special case is presented by carriers in the venereal dis- 
eases. Recently a demand for premarital examinations has arisen 
to meet this situation. In spite of its difficulties this movement is 
a real advance. It calls for examinations for syphilis, including 
the Wassermann reaction, and examination for the gonorrhea, 
including specimens of prostatic secretions. If these examina- 
tions were more general and if appropriate action followed the 
results, the number of social tragedies and divorces would be 
appreciably reduced. 

3. CARRIER WORK IN THE MILITARY SERVICES 

On the technical side, carrier work in the military services is 
of course the same as elsewhere, as the putting of a uniform on the 
host does not affect the parasite. There are, however, several 
special factors in epidemiology and administration among soldiers 
which do affect the work in a peculiar way. Personal contact is 
much closer and more constant among troops in barracks or in the 
field than among private citizens. Hence, the chances for the 
functioning of carriers are particularly good. On the other hand, 
diagnostic and control measures, when approved, can be carried 
out more exactly on account of military discipline. Again, the 
high standard of laboratory facilities which has been maintained 
in the United States Army since the days of Sternberg tends to 
make carrier work easier than in some other places. It may, 
therefore, be said that conditions in the Army, and the same is 
true of the Navy, offer unusual need and opportunity for carrier 
work. The drawbacks are lack of time for proper examination, 
lack of facilities for the mass of work and lack of control due 
either to an emergency or to official non-support. 

Beginning with the case, release examinations can usually be 
made with certainty. Regulations insure the sending of speci- 
mens to the laboratory and the laboratory work is usually prompt 



PHOROLOGY AND PREVENTIVE MEDICINE 117 

and reliable. In fact, three release cultures of feces and urine 
after typhoid infections have been made for years in the Army 
as a result of the early efforts of Russell. The Malarial Register, 
introduced by Craig, has also served to emphasize the carrier 
aspects of malaria. Release cultures are also of course made 
routinely in convalescents from diphtheria and should be the 
rule after meningitis, dysentery and cholera. 

After an epidemic, the number of temporary convalescent 
carriers may be so large as to be a problem. It may be necessary 
to send men to duty as soon as possible, but carriers should be 
held if possible until clean. The alternative of discharge for 
disability should be taken only as a last resort. A public service 
owes it to the individual and to the country to do as much as pos- 
sible for the carrier state. If discharge becomes necessary, the 
public health officials of the place to which the man goes should 
be notified. 

Recruits offer a large opportunity for carrier work. It is being 
realized more than ever that the raw recruit is first of allamedical 
problem. He should be examined for mental and physical suita- 
bility; minor defects should be corrected. He should be immu- 
nized against smallpox and the typhoid fevers. Wassermann 
reactions have been done routinely in the past and Schick tests 
are now in order. Altogether about two weeks time could be 
taken up by the medical officers in preparing the recruit for the 
work in hand. The preparation of a recruit's tissues by the cor- 
rection of defects and the training of his immune mechanism by the 
medical officer is as necessary as the training of his neuromus- 
cular apparatus or his morale by the line officer. Carrier work 
is another measure of preparation for social enterprises. The 
detection of carriers should be done early in order to pick up 
chronic convalescent carriers before any harm is done. On 
account of the numbers, it may be necessary to confine the 
examination to those who give a previous history of diphtheria, 
meningitis, typhoid or dysentery or malaria, or who come from 
infected districts. 

When cases occur, the examination of contacts is indicated, but 
its degree of application is a difficult question. A complete ex- 
amination is of course the logical measure, but it is usually out of 



118 CARRIERS IN INFECTIOUS DISEASES 

the question and practical experience shows that other less radical 
measures are sufficient. Attempts to examine contacts should 
usually be confined to immediate contacts only, unless the group 
is small, or unless the laboratory facilities are unusual, or unless 
other measures fail, such as general sanitation and hygiene. 

In any effective carrier work, some continuous record is neces- 
sary by which a chronic carrier can be checked up by different 
medical officers under whose observation he may come. In the 
Navy, the Health Record would serve admirably for this purpose. 
The Army has as yet no record of this kind, except the Syphilitic 
and Malarial Registers. Efforts to introduce a Health Record 
have so far been defeated by the amount of work necessary for 
keeping it properly. There is, however, the individual Service 
Record which has in the past had some data on vaccination. It 
has now been decided to give more space for medical records which 
will include a place for carrier examinations. In this way the car- 
rier status of the individual can be checked up by each medical 
officer who reviews the records. 

During the war, carrier work eventually reached a high state of 
technical perfection as so many well trained medical officers and 
assistants were available. The degree to which the carrier pro- 
gram was actually used to control the situation varied with the 
circumstances. Now that the military establishments are con- 
tracted to a peace basis, this work has necessarily become limited. 
But since the work of the military organizations is now largely 
educational in connection with National Guard and the Reserves, 
the principles learned should not be forgotten. This new knowl- 
edge should be applied on as large a scale as possible, as a measure 
of education and preparation. 



PART IV 

CARRIERS IN VETERINARY 
MEDICINE 



CARRIERS IN VETERINARY MEDICINE 

Carriers of the specific organisms of various infectious diseases 
met with in veterinary medicine have for a number of years been 
recognized among domestic animals. However, there is a marked 
paucity of literature treating of the subject generally. As a 
matter of fact, so far as I have been able to ascertain, there is not 
a single work published in English, French or German, dealing 
collectively with carriers of disease-producing organisms of veteri- 
nary subjects. 

On the other hand, the carrier problem in a number of infectious 
maladies of domestic animals has been given careful consideration 
in studies of the individual diseases, and from our present know- 
ledge of the subject, thus gained, it is clearly evident that carriers 
among veterinary subjects present a problem equal in impor- 
tance to that in human medicine. Further, in numerous in- 
stances the animal carrier is a distinct menace to the health of 
human beings, so that often the problem is not only one of pre- 
vention of disease among lower animals, but of safeguarding the 
health of man as well. 

For purpose of consideration in this section, carriers have been 
arranged in three principal groups. The first group includes 
carriers of organisms known to be pathogenic for man as well as 
for the lower animals. The second group deals with carriers of 
organisms which are pathogenic for lower animals and which may 
possibly prove pathogenic for man under certain circumstances. 
The third group includes carriers of organisms pathogenic for 
animals only. Under each main group are then taken up (1) 
carriers of bacteria, (2) carriers of protozoa and (3) carriers of 
filterable viruses. 



121 



CHAPTER XVII 

Carriers of Organisms Pathogenic for Both Man and 
The Lower Animals 

a. carriers of bacteria 

1. Micrococcus melitensis 

"Mediterranean," "Rock/' "Undulant" or "Malta" fever in 
man, caused by Micrococcus melitensis, has for an indefinite 
period been more or less endemic on the Island of Malta. The 
disease has also been reported from Italy, Greece, Turkey, Spain, 
India, Africa and the Philippine Islands. In the United States 
it has occured in Texas along the Mexican border. The affection 
is primarily a disease of goats. Sheep, horses and cattle, however, 
are occasionally affected. 

From the standpoint of carriers, Malta fever presents a highly 
important problem in those localities where the disease exists, as 
the infection is ordinarily transmitted to man through the inges- 
tion of milk from animals harboring Micrococcus melitensis in 
their udders. 

Zammit (1) demonstrated that approximately 10 per cent of 
the goats on the Island of Malta, though apparently healthy, 
were eliminating the micrococcus of Malta fever with their milk. 
Such milk, when fed to monkeys, even for one day, produced 
typical attacks of the disease, the manifestations of the affection 
in such animals closely resembling the sj-mptoms noted in the 
disease in man. 

Carriers also eliminate the organism irregularly in their urine. 
The disease may thus be readily transmitted to healthy animals 
through the ingestion of feed and water contaminated with the 
urine of carriers. 

Mohler and Hart (2), in reporting the finding of carriers in an 
importation of 65 goats from the Island of Malta to the United 
States in 1905, state that out of 12 persons who were known to have 

123 



124 CARRIERS IN INFECTIOUS DISEASES 

consumed milk from these goats during the voyage to this country, 
8 developed Malta fever. The diagnosis was confirmed in 5 
cases by the agglutination test, blood specimens not being obtained 
from the other 3 cases. The 4 individuals who failed to contract 
the disease drank only a small amount of the milk or partook of 
it only after it had been heated. 

Upon arrival in the United States the goats in this shipment 
were placed in quarantine and specimens of their blood serum 
subjected to the agglutination test for Malta fever. Twenty 
positive and suspicious reactions were obtained. Subsequently 
positive results were obtained with specimens from a number of 
those animals whose blood had given negative results to the first 
test. 

The milk of 8 typically positive reactors was examined bacterio- 
logically and Micrococcus melitensis demonstrated in large num- 
bers in 4 cases. The milk of these animals appeared absolutely 
normal and failed to show evidence of changes even on chemical 
examination. Examination of the urine revealed the organism 
in 1 out of 11 cases studied. 

Habitat of the organism. Micrococus melitensis in the body of 
carriers lives a passive existence. In localities where the disease 
is prevalent a large percentage of goats, and in some instances 
sheep, harbor the organism in their udders, usually without 
changes in the gland tissue. In a number of cases the micrococcus 
is also found in the blood of apparently healthy animals and is 
eliminated in the urine. Rarely the organism is found in the 
intestinal tract. 

Occasionally autopsy of carriers of the organism may demon- 
strate a slight fibrinous inflammation of the udder and in some 
few cases purulent foci. The spleen and certain of the lymph 
nodes, particularly the mesenteric and inguinal glands, may be 
found slightly swollen. 

Detection and management. Carriers of Micrococcus melitensis 
may be detected through the application of the agglutination test 
and bacteriological examination of the milk, blood and urine of 
suspected animals. Saisawa (3) utilized the complement-fixation 
test for the detection of the infection. However, because of its 
relative simplicity, the agglutination test is more adaptable. 



ORGANISMS PATHOGENIC FOR MAN AND ANIMALS 125 

In carrying out the agglutination test either blood or milk serum 
may be used. Blood serum, however, is preferable. Mohler and 
Hart (2), after comparing the agglutinating titre of blood serum 
from normal and infected goats, considered complete agglutina- 
tion within one and one-half hours in a dilution of at least 1 : 70, a 
positive reaction. 

Several years ago Evans (4), in calling attention to the very 
close relationship of Bacterium abortus (Bang) to Micrococcus 
melitensis, pointed out that the serum of cattle infected with the 
Bang organism readily agglutinates the micrococcus of Malta 
fever. While at present there is no evidence that goats are com- 
monly infected with Bact. abortus, the possibility of positive 
reactions in some instances being due to infection with the bac- 
terium of Bang, should be borne in mind when carrying out the 
agglutination test for Malta fever. 

For the bacteriological examinations a nutrose agar containing 
beef serum and of a slightly acid reaction, is best adapted for the 
isolation of the organism. The growth, however, is rather slow. 
Seventy-two hours or longer are required before the colonies are 
discernible to the naked eye. 

Animals found to be carriers of Micrococcus melitensis are a 
menace to the health of both man and animals. In local- 
ities where the disease is not well established its spread should be 
guarded against by the prompt destruction of cases and carriers. 

Where the disease is well established and a great number of the 
animals are infected, slaughter of carriers is not always feasible. 
In such cases the disease can only be controlled by the inaugura- 
tion of measures to prevent direct or indirect contact of carriers 
with healthy animals. 

As the disease in man is due, in essentially all instances, to the 
consumption of milk containing the organism, it is highly im- 
portant that milk from known or suspected carriers of Micrococcus 
melitensis be properly pasteurized. 

2. Bacillus tuberculosis 

The disseminator of bovine tubercle bacilli is a serious menace 
to the health of man because of the susceptibility of young persons 
to infection with this type of the organism. In the vast percen- 



126 CARRIERS IN INFECTIOUS DISEASES 

tage of cases the infection is transmitted through milk. Trans- 
mission of tuberculosis from animal to man through the ingestion 
of infected meat, or meat-food products into the preparation of 
which may have entered glands or other tissues containing the 
organism, is very rare. In the first place the large percentage of 
meat consumed is cooked. Further, meat does not form a part of 
the ordinary diet of young children. Where eaten uncooked by 
adults, chance of infection is slight, because of the resistance of older 
persons to the infection with the bovine type of tubercle bacilli. 
Where vaccination of animals with human tubercle bacilli, as later 
described, is attempted, we have a different situation. In such 
instances the organism eliminated by vaccinated animals is capable 
of producing tuberculosis in both children and adults. 

In tuberculosis we frequently meet with cattle which clinically 
manifest themselves as carriers but which are in reality occult 
cases of the disease. Such cases are often noted among dairy 
cows. Animals apparently in the pink of condition have been 
known to eliminate tubercle bacilli with their milk intermittently 
for years, the only indication of disease being a positive response 
to the tuberculin test. In other cases of this character tubercle 
bacilli are eliminated periodically for years with the feces, as a 
result of an occult pulmonary affection. In such instances the 
animal swallows material from the lungs containing the organism 
and passes it through the digestive tract. Autopsy of these cases 
demonstrates open lesions of a progressive nature. Animals 
coming into this category, when permitted to live for a consider- 
able time, as a rule, subsequently manifest evidence of the disease 
and on autopsy well-marked lesions of tuberculosis, frequently 
generalized, are found. These cases cannot, therefore, be con- 
sidered true carriers. 

There is another condition met with in cattle in which certain 
animals may more properly be considered true carriers of the 
tubercle bacillus. Not infrequently, autopsy of cattle which 
have reacted to the tuberculin test, fails to demonstrate appreci- 
able lesions of tuberculosis. Bacteriological examination and 
guinea pig inoculations, however, frequently demonstrate that 
certain of the lymph glands of such animals, while appearing nor- 
mal, or at the most showing only minor changes, harbor the bacil- 



ORGANISMS PATHOGENIC FOR MAN AND ANIMALS 127 

lus of tuberculosis. Of 1296 specimens, practically all of which 
were such lymph glands, examined by the United States Bureau of 
Animal Industry (5) during the fiscal year 1921, a total of 258 or 
nearly 20 per cent were found to harbor tubercle bacilli. Such 
carriers are not a menace as disseminators of the infection, but 
are of importance from the standpoint that they may later pass 
from what might be termed an "incubationary carrier" state, 
develop the disease in a pronounced form, and then become 
spreaders. 

Carriers of tubercle bacilli may be produced in dairy cows as a 
result of attempts at artificial immunization against tuberculosis. 
Some years ago considerable attention was paid by investigators 
of animal diseases to the so-called "bovo-vaccination" of cattle 
against tuberculosis. The treatment consisted of the intravenous 
administration of human tubercle bacilli which were not fully 
virulent, cattle possessing considerable resistance to the human 
type of organism. \3Vhile such procedure materially raises the 
immunity of the animal to bovine tuberculosis, a large percentage 
of such cattle were found to harbor and eliminate the organism 
from their udders for years, without developing manifest lesions 
of the disease themselves, or at the most developing very minor 
lesions after tolerating the organism for a long period of time. 
Because of these dangerous carriers, produced as a result of this 
method of vaccination, the procedure did not become established 
in the United States. 

The tubercle bacillus is frequently found in various of the 
lymph glands of hogs, occurring without additional lesions in 
other organs. In some such cases little or no abnormality is 
noted in the gland structure. In other cases, however, marked 
changes are found. Thus, as scrofula is a rather characteristic 
form of the disease in hogs, it is difficult to distinguish between 
what might properly be termed a carrier and an early case of 
tuberculosis of the glands. The bacillus of tuberculosis has also 
been occasionally found in the tonsillar crypts in hogs. Their 
presence in such location, however, is usually transitory. 

Habitat of the organism. In those carriers among cattle which 
harbor the tubercle bacillus in glands, the submaxillary, cervical, 
prescapular, mediastinal, bronchial and mesenteric nodes are the 



128 CARRIERS IN INFECTIOUS DISEASES 

most frequent locations. Such glands may be more or less swollen 
and show small inflamed areas in the cortical substance. 

In carriers produced as a result of vaccination against tuber- 
culosis no detectable lesions may be found on autopsy, although 
the animal may have been eliminating the organism frequently 
with her milk. However, after a considerable period of time (3 or 
4 years in some instances) small atypical tubercles may be found 
in the udder. 

In hogs the submaxillary and superior cervical glands are favor- 
ite habitats of the organism. The bronchial, gastro-hepatic and 
mesenteric glands are less frequent locations. Where these glands 
show lesions, a type of hyaline degeneration is frequently seen, 
cross sections of such glands having a dendritic or arbor-vitae 
appearance. In other instances small areas of inflammation or 
small yellow foci may be demonstrated in the glands. 

Detection and management. The subcutaneous, intradermic or 
ophthalmic tuberculin tests, or combinations of the same, consti- 
tute the only means at our disposal for the detection of the carrier 
type of animal harboring Bacillus tuberculosis in its glands. 
Obviously, however, such tests will not differentiate these carriers 
from the more marked cases of tuberculosis. Further, while a 
considerable percentage of animals carrying the organism in their 
lymph glands will respond to the tuberculin test, negative results 
are undoubtedly obtained in a percentage of such cases. 

Where vaccination against tuberculosis has been practiced, 
bacteriological examinations and guinea pig inoculation tests with 
milk specimens from suspected carriers, prove satisfactory for 
their detection. These tests must be frequently repeated, how- 
ever, where negative results are obtained, before concluding that 
the animal is not eliminating the organism. Some of these car- 
riers will also give a positive response to the tuberculin test. 

The prompt slaughter of cattle and hogs known to harbor the 
tubercle bacillus is the practice to be recommended. Except in 
cases of valuable breeding stock, such hogs would ordinarily be 
butchered as an economic procedure. With cattle, however, this 
method cannot always be carried out because of the common 
practice of a large number of dairymen to maintain herds con- 
taining tuberculous cows. Under such conditions rigid measures 



ORGANISMS PATHOGENIC FOR MAN AND ANIMALS 129 

should be taken to prevent the exposure of healthy animals to these 
carriers of tubercle bacilli. 

Because of the pathogenicity of the bovine type of tubercle 
bacillus for children, and the part that milk can play in the trans- 
mission of the infection, pasteurization of milk from herds in 
which there are animals known or suspected of harboring the 
bacillus of tuberculosis is obviously of utmost importance. 

3. Organisms of the Salmonella, Enteritidis or Gaertner group 

Bacillus enteritidis (Gaertner), Bacillus paratyphosus "B," 
Bacillus suipestifer, Bacillus aertrycke, and other members of the 
Salmonella group, have at different times been found associated 
with a variety of pathological conditions in cattle, horses, sheep, 
hogs and other animals. Further, carriers of these organisms 
have been frequently found among animals which have recovered 
from such affections, as well as in animals with no history of dis- 
ease. Because of the role organisms of this group play in the 
production of "food-poisoning" in man, carriers of the same are 
of particular importance. 

B. enteritidis has been occasionally found associated with severe 
cases of dysentery, especially in calves, although adult cattle 
are sometimes affected. Mohler and Buckley (6) in 1902 found 
B. enteritidis to be the etiological factor in an outbreak of enteritis 
with marked symptoms of intoxication, in a stable of twenty-one 
cows. This organism has also been found in pathological condi- 
tions of the udder, persisting in some cases for considerable periods 
of time after the disease process has subsided. 

In hogs, Bacillus suipestifer is found as a complicating factor 
in cholera, the primary cause of the disease being a filterable virus. 
Carriers of this bacillus are very frequently found. 

Among experimental animals the writer has noted an outbreak 
of disease among guinea pigs due to Bacillus aertrycke, in which 
carriers of the organism were subsequently found. O'Brien (7) 
records an epizootic among stock guinea pigs at the Lister Institute 
due to an organism which he identified as B. suipestifer. Subse- 
quent to the outbreak he demonstrated 5 of the recovered animals 
to be carriers, eliminating the organism intermittently for five 
months. 



130 CARRIERS IN INFECTIOUS DISEASES 

Members of this group of organisms are occasionally responsible 
for outbreaks of disease among rodents. Further, healthy rats 
and mice are often found to be carriers of the bacilli of this group, 
eliminating the same with their feces. Because of the opportunity 
afforded for the contamination of foodstuffs with fecal matter 
from rats and mice around abattoirs, refrigerator plants, butcher 
shops, etc., these carriers are of no little importance. 

Heuser (8) examined 100 mice and found 5 or 5 per cent har- 
boring B. enteritidis and B. paratyphosus "B." Zwick and 
Weichel (9) in examining 177 mice demonstrated 28 or nearly 
16 per cent to be carriers of organisms of the Salmonella group. 

Meissner, Berge and Kohlstock (10) report an interesting out- 
break of dysentery among calves due to B. enteritidis. One of the 
recovered animals was placed in a pasture with a number of cows 
and shortly thereafter the disease broke out among the adult 
animals. The recovered calf was then examined and was found 
to be harboring B. enteritidis in its intestinal tract. 

Outbreaks of food-poisoning in man in a number of instances 
have been definitely traced to animals disseminating organisms of 
this group. Savage (11) described an outbreak of food-poisoning 
occurring at Newcastle-under-Lyme in 1914, in which 468 cases 
with 2 deaths occurred. The malady was found to be due to B. 
enteritidis in milk consumed by the affected individuals. Inves- 
tigation proved the source of the infection to be a cow which had 
recently calved, and which had an udder affection and abscesses 
in one of its legs. The serum of this animal readily agglutinated 
B. enteritidis. Subsequent examination demonstrated B. enter- 
itidis in the urine and uterine discharge. After the outbreak a 
number of specimens of milk from this cow were examined and on 
two occasions B. enteritidis was isolated. 

Aside from those cases in which organisms of the enteritidis 
group may be eliminated with the milk, contamination with fecal 
matter often occurs at the time of milking through the dropping 
of particles of manure from the hair of cows which have not been 
properly cleaned, or through splashing at the time of defecation. 

As regards meat, ample opportunity is often afforded for fecal 
contamination of such food in the slaughter-house during the 
course of its preparation. Thus carriers harboring members of 



ORGANISMS PATHOGENIC FOR MAN AND ANIMALS 131 

this group of organisms in their intestinal tracts may infect their 
own tissues or those of other animals at the time of slaughter, 
thereby indirectly menacing the health of man. 

Habitat of the organism. In the larger percentage of cases, 
carriers of organisms of the Salmonella group harbor the same in 
their intestines, usually without appreciable tissue changes in the 
carrier state. Occasionally, small necrotic foci containing organ- 
isms of this group have been demonstrated in the spleen and liver 
of cattle, sheep and hogs. 

In hogs which have had the intestinal form of cholera, ulcers 
of variable size (lental to as large as a quarter) which are slow to 
heal, and which usually harbor B. suipestifer, are often found, 
especially in the caecum and large intestine. These ulcers usually 
occur as round, slightly projecting masses, of a yellow, brown, or 
almost black color, the cut surface appearing laminated from the 
periphery towards the center. Microscopically, sections cut per- 
pendicularly through the ulcer show the thickened submucous 
tissue to contain numerous dilated capillaries and a large number 
of round cells. Above this is a thin layer of deep staining amor- 
phous material. The uppermost layer is made up of necrotic 
material containing large numbers of bacteria of different type. 
B. suipestifer may be found in the necrotic material and frequently 
in large numbers around the periphery of the ulcer between the 
necrotic and healthy tissue. 

Organisms of this group are occasionally found in the udder, 
usually following some type of udder trouble for which it was 
responsible, and rarely when there is no history of disease. Where 
such carriers have had a pathological process in the udder, tissue 
changes, characteristic of previous glandular inflammation, fre- 
quently exist. 

In the B. aertrycke infection noted by the writer the organism 
was found harbored in the gall bladder. The walls of the bladder 
in most instances showed a marked catarrhal thickening. 

Detection and management. Carriers of bacilli of the Sal- 
monella group, harboring the same in their intestinal tracts and 
udders, as a rule, may be detected through the employment of 
ordinary bacteriological methods. Repeated examinations, how- 
ever, must be made in some instances before the organism can be 



132 CARRIERS IN INFECTIOUS DISEASES 

demonstrated. The agglutination test may prove of some help 
in identifying animals suspected of carrying certain members of 
the group. Further, the writer was able to obtain complement- 
fixation reactions with blood serum from guinea pigs harboring 
B. aertrycke in their gall bladders. 

Animals known to be carriers of organisms of the Salmonella 
group which are capable of producing disease in other animals, 
should be kept isolated until they are proven no longer a menace. 
In cases in which the organism is carried in the udder, irrigation 
with mild antiseptics may prove of value in eliminating the foci 
of infection. Occasionally bacterins or vaccines give good results. 
Administration of intestinal antiseptics has been resorted to in an 
effort to eliminate offending organisms harbored in the intestines. 
Such treatment, however, is not particularly promising of results. 
The slaughter of persistent carriers which continually cause 
trouble, is sometimes the most economic procedure. 

Particular consideration should be given to measures for the 
prevention of infection of man. Milk from cows harboring 
organisms of this group is a particularly dangerous food for 
both man and animals. It should be remembered that Bacillus 
enteritidis (Gaertner) produces a toxin which is unaffected by 
pasteurization. 

Because of the possibility of milk becoming contaminated with 
particles of fecal matter, during the milking process, cows know 
to carry organisms of the Gaertner group in their intestinal tracts 
are dangerous animals to supply milk for human use and should 
be eliminated as a source of milk supply while thus harboring and 
eliminating these organisms. 

In the slaughtering of food-producing animals every precaution 
should be taken to prevent the contamination of carcasses with 
fecal matter. Particular attention should be given to measures to 
prevent meat and other food products from becoming contami- 
nated with the excrement of rats and mice. 

4. Bacillus tetani 

The horse is a well-known carrier of Bacillus tetani. Cattle, 
sheep and hogs, however, also harbor the organism in their intes- 
tinal tracts and eliminate the same in considerable numbers in 



ORGANISMS PATHOGENIC FOR MAN AND ANIMALS 133 

their feces. Further, it has been demonstrated that the tetanus 
bacillus is not infrequently carried by smaller experimental ani- 
mals (rabbits and guinea pigs). The organism has a very exten- 
sive distribution in nature, being a common inhabitant of the 
soil, especially where the same contains manure, particularly that 
from horses. 

It is the opinion of some investigators that soil contains the 
organism only after receiving deposits of manure from horses or 
other herbivora harboring B. tetani, or where it is indirectly con- 
taminated with drainage from areas containing manure of such 
carriers. This, however, is not likely. Because of the large 
percentage of carriers among herbivora, the tetanus bacillus is 
found more abundantly in earth containing manure, but it is 
nevertheless found in soil undoubtedly free from such fecal 
contamination. 

The percentage of carriers among animals in different locations 
varies between rather wide limits. Park and Williams (12) state 
that approximately 15 per cent of horses and calves in the vicinity 
of New York City harbor the tetanus organism in their intestines. 

On various stock farms it is often notable that tetanus almost 
invariably follows minor wounds not properly treated. In other 
localities such occurrence of the disease may be extremely rare. 

Habitat of the organism. In carriers Bacillus tetani is found in 
the intestinal tract, especially in the large intestine. As is the 
case with a number of organisms harbored in the intestines, the 
tetanus bacillus under normal conditions, causes no disturbance in 
the health of its host and produces no change in the intestinal 
tissue. 

While the horse commonly harbors B. tetani it is, nevertheless, 
very susceptible to tetanus. This type of carrier, in a way, is a 
mechanical carrier, as differentiated from the immune and con- 
valescent types. 

Detection and management. No particular difficulty is experi- 
enced in demonstrating the tetanus bacillus in the excreta of car- 
riers by bacteriological examination and through the inoculation 
of mice, guinea pigs or rabbits. 

It is obvious, of course, that with tetanus we are confronted with 
an organism which exists practically everywhere and of which 



134 CARRIERS IN INFECTIOUS DISEASES 

thousands of carriers exist and are coming into being daily. It 
is, therefore, highly important that particular attention be paid 
to wounds which have directly or indirectly come in contact with 
manure and soil or admixtures of the same. 

5. Bacillus oedematis maligni ("Vibrion septique") 

The anaerobic Bacillus oedematis maligni, or " Vibrion septique' ' 
as it was called by Pasteur, is widely distributed in nature and is 
frequently found in the intestinal tracts of normal cattle, horses, 
sheep and hogs. 

Among animals, malignant edema, the specific disease of this 
organism, frequently results from the infection of contused, 
lacerated, incised and other types of deep wounds, with soil, feces 
of carriers, or other material containing the bacillus of malignant 
edema. The disease sometimes follows castration and shearing. 
Further, it is an occasional complication of difficult parturition, 
where help is given the animal and proper precautions are not taken 
to prevent the introduction of infection with the hands and in- 
struments. The disease also occurs in man following the con- 
tamination of wounds with soil, manure, or admixtures of the 
same. 

Habitat of the organism. Carriers of Bacillus oedematis maligni, 
as stated above, harbor the organism in their intestinal tracts. 
Under normal conditions the bacillus lives a purely saprophytic 
existence in the intestines of such carriers, producing no tissue 
changes whatever as a result of its presence there. 

Detection and management. The bacillus of malignant edema 
can usually be demonstrated in the feces of carriers through ana- 
erobic cultural methods and animal inoculation tests without 
difficulty. 

As this organism is found constantly in soil and is carried by 
a large number of animals of different species, sanitary measures 
must be relied upon to control the infection, as the elimination of 
carriers is obviously impossible. Particular attention should be 
paid to severe wounds contaminated with manure or soil. 



ORGANISMS PATHOGENIC FOR MAN AND ANIMALS 135 

6. Bacillus anthracis 

While at the present time nothing is known of possible carriers 
of the anthrax organism among cattle, horses and sheep, it has 
been definitely established that apparently healthy hogs occa- 
sionally harbor Bacillus anthracis in various of their lymph glands. 

Fortunately, the organism thus localized is not capable of being 
eliminated continuously to the outside world. However, such 
carriers are, nevertheless, of considerable importance; first, be- 
cause they may later develop the disease in an acute form, thus 
disseminating the infection, and secondly, because such glands 
entering into the preparation of "cured" meat-food products, may 
produce the disease in man consuming such food, especially when 
uncooked. 

Habitat of the organism. In hogs harboring Bacillus anthracis 
the organism is found most frequently in the mesenteric group, 
often only a single gland in the group being affected. Less fre- 
quently the cervical glands may be the seat of the infection. Oc- 
casionally the bacillus may be demonstrated in the submaxillary 
glands. 

Glands containing the anthrax organism, as a rule, are more or 
less enlarged, and on cross section they appear of a brick-red color 
or they may be permeated with small, grayish-yellow, necrotic 
foci. The surrounding connective tissue may disclose a sero- 
edematous infiltration. 

Detection and management. In the absence of allergic or other 
specific tests for anthrax, it is impossible to detect, during life, 
hogs which may be carrying the anthrax organism in their lymph 
glands. Consequently we are without means to prevent the 
possible introduction of such carriers in the midst of healthy hogs. 

When carriers of this character are butchered in establishments 
where meat inspection service is maintained, the veterinary in- 
spector has the opportunity to detect some of those cases which 
show appreciable lesions of the glands. However, in some in- 
stances the tissue lesions are so insignificant they may escape 
detection. It is obvious, therefore, that in order to prevent the 
possible infection of man, the added safe-guard afforded by thor- 
oughly cooking various "cured" products before consumption, is 
advisable. 



136 CARRIERS IN INFECTIOUS DISEASES 

7. Bacillus mallei 

While no definite, clear-cut carrier problem has been recognized 
in glanders, this disease is one of those maladies in which it is 
occasionally difficult to determine whether or not a particular 
infection can properly be placed in the category of carriers. 

Autopsy of animals which have reacted to the allergic or sero- 
logical tests for glanders, frequently reveal in the lungs, and 
occasionally in the liver or spleen, glanders nodules in an inactive 
or apparently arrested stage. Sometimes only a single nodule of 
such character is found. Very frequently it is impossible to 
isolate B. mallei from some of these lesions. On the other hand, 
in some of these arrested cases it is possible to demonstrate the 
organism bacteriologically and through guinea pig inoculation. 
In such case we are possibly justified in concluding that the animal 
in which this type of lesion was found was a carrier. Should it 
have been permitted to five and mingle with other animals it 
may have subsequently initiated an outbreak of glanders through 
development of the disease in an active, communicable form from 
this focus. 

Habitat of the organism. In such instances, as described above, 
the lesions are most commonly found in the lungs. However, 
thejr are occasionally found in the fiver or spleen. They occur as 
small, gray, shining nodules, rarely larger than a pea, the center 
often appearing pale yellow as a result of necrosis. The nodule is 
walled off from the normal structure by fibrous tissue. 

It is often very difficult to differentiate the nodule of glanders 
from those caused by parasites. Microscopically, however, eo- 
sinophilia is a characteristic finding in parasitic nodules. Fur- 
ther, in parasitic nodules of recent origin fragments of the parasite 
may often be demonstrated, while in older processes there is usu- 
ally calcification. Calcification in glanders nodules is doubtful, 
a number of investigators maintaining that it never occurs. It 
is certainly not a common finding. Demonstration of B. mallei 
in the nodule, of course, definitely establishes its nature. Failure 
to demonstrate the organism, however, would not in itself prove 
that the lesion was not that of glanders but obviously eliminates 
it from consideration as a carrier lesion. 



ORGANISMS PATHOGENIC FOR MAN AND ANIMALS 137 

Detection and management. The allergic and serological tests 
must be depended upon for the detection of carriers of Bacillus 
mallei as here considered. Fortunately, these tests give excellent 
results in the great percentage of cases. They do not, of course, 
differentiate between the active and arrested case. However, as 
the destruction of both active and inactive cases is advisable, this 
shortcoming of the diagnostic methods at our disposal, is of little 
consequence. 

Suspected animals should be tested with intradermic or ophthal- 
mic mallein, and in the case of suspicious or doubtful reactors, 
serum specimens from the questionable animals should be sub- 
jected to the complement-fixation and agglutination tests for 
glanders. A positive reaction to any one of these tests warrants 
the destruction of the animal. 

8. Bacillus diphtheriae 

While it has been proven beyond all doubt that true diphtheria 
in man and the common diphtheritic affections of lower animals, 
are distinct and separate entities, diphtheria due to infection with 
the Klebs-Loeffler bacillus occasionally occurs in animals coming 
in contact with individuals of the human family suffering from the 
disease. Considerable reference is made in the literature to 
cases of diphtheria occurring in cats, dogs, fowls, etc., as a result 
of infection with the organism of human diphtheria. Further, 
occasional transmission of the disease from animal to man has 
undoubtedly occurred. 

From the standpoint of carriers, the house cat has been fre- 
quently incriminated. No information, however, is available 
as to the possible length of time the organism may persist in the 
body of such carrier. 

Savage (13) has pointed out that diphtheria-like organisms 
may often have been taken for the real diphtheria bacillus 
in reports of cases and carriers of the infection among cats 
where the bacteriology of the case was not thoroughly worked out. 
He even goes so far as to conclude that it has not been satisfac- 
torily established that cats develop diphtheria due to the Klebs- 
Loeffler bacillus or are carriers of the infection. There is, however, 
ample evidence of a definite nature to refute such conclusions. 



138 CARRIERS IN INFECTIOUS DISEASES 

Simmons (14) reports a fatal case of diphtheria in a woman, 
apparently contracted from a cat which was permitted to sleep 
in her bed. The cat had been sick about a week before the woman 
became ill. It had a croupy cough, was unable to swallow food 
and continually cried. The condition persisted for approximately 
two weeks after which the animal appeared to improve. Cultures 
from the throat of both the woman and cat demonstrated the 
presence of Klebs-Loeffler bacillus, the identity of the organism 
in both instances being definitely established through immuno- 
logic tests carried out with guinea pigs protected with diphtheria 
antitoxin. The cat was chloroformed and autopsied and B. 
diphtheria recovered from a lesion in the nasal fossa. 

A second cat which had been associated with the animal just 
referred to, was found to harbor true diphtheria bacilli in lesions 
of the vocal cords. 

Habitat of the organism. Cats which are found to be carriers 
of the Klebs-Loeffler bacillus, harbor the organism in their nose or 
throat. In one of the two cases described by Simmons, a small 
oval ulceration, covered with a yellowish-gray pseudomembrane, 
occurring between two smaller red inflammatory areas, was noted 
in the left nasal fossa. In the second case described by this au- 
thor, small, elongated, grayish-white patches of pseudomembranes 
were found covering ulcerations of the vocal cords. These patches 
were surrounded by a red inflammatory zone. 

Detection and management. In examining cats suspected of har- 
boring the diphtheria bacillus, material should be obtained from 
the throat and each side of the nose with sterile swabs and 3 or 4 
tubes of Loeffler's serum media inoculated with each swab. These 
cultures should then be incubated and subjected to the usual 
bacteriological examination for Bacillus diphtheriae, care being 
taken not to mistake pseudo-diphtheria organisms, frequently 
found, for the Klebs-Loeffler bacillus. 

Cats demonstrated to be carriers of the organism of human 
diphtheria are obviously a menace to the health of human beings, 
especially the child who plays with the animal. Although there 
are no records of the isolation and treatment of such carriers, it 
is probable that a number of these cases would clear up under 
proper treatment. However, under ordinary circumstances, 
prompt destruction of recognized carriers is the policy to follow. 






ORGANISMS PATHOGENIC FOR MAN AND ANIMALS 139 

9. Bacillus pestis 

While bubonic plague ordinarily occurs as an acute affection in 
rats, in localities where the disease is endemic apparently healthy 
rats may occasionally be found harboring Bacillus pestis in foci 
in their abdominal viscera. 

The Indian Plague Commission (15), in examining a large 
number of rats caught in two villages where plague had recurred 
annually without discoverable reinfection, found 6 apparently 
healthy animals with small abscesses in their abdominal cavities, 
containing virulent plague organisms. These rats were all trap- 
ped within two months, at a time of the year when, so far as could 
be ascertained, plague did not exist in man nor rats in the two 
villages in question. 

McCoy (16) found 13.8 per cent of several hundred ground 
squirrels examined for plague lesions, harboring B. pestis in puru- 
lent foci in one or more lymph glands, with no additional evidence 
of disease. In squirrels experimentally infected, similar lesions 
(referred to by McCoy as "residual buboes") were observed in the 
majority of animals which survived the infection. 

Rats and squirrels with such lesions have ordinarily been 
looked upon as chronic cases. Nevertheless, without drawing the 
line too close, the animal with small, entirely localized lesions of 
an inactive character, which give rise to no manifest disturbance 
of health, may properly be considered a type of carrier. 

From present knowledge, it is difficult to say just how much 
importance should be attached to such carriers of Bacillus pestis. 
Apparently they are not a serious menace. Whether or not the 
organisms persisting in these abscesses are ever capable, under 
certain conditions, of subsequently inciting an acute attack of 
plague, thus permitting of its spread, is a matter of conjecture. 
However, the carcasses of rats with such lesions, dead from 
some other cause, may be eaten by susceptible rats and thus give 
rise to an outbreak of the disease. 

Habitat of the organism. The lesions of Bacillus pestis in rats 
harboring the organism, are usually found in the spleen, liver, 
mesentery and pelvic glands. They occur as small abscesses con- 
taining a creamy or cheesy pus. Often adhesions are found 
between the affected area of the spleen and the mesentery. 



140 CARRIERS IN INFECTIOUS DISEASES 

In squirrels, McCoy found the median, posterior inguinal 
and pelvic glands the most frequent seat of the infection. Less 
frequently lesions were found in the cervical and axillary glands. 
The gland may appear as a mass of slightly yellowish pus as large 
as a pea. In other instances the purulent mass is much smaller, 
or there may be noted only a few, mustard-seed size, necrotic 
points. 

Detection and management. Rats and squirrels harboring the 
plague organism in these chronic lesions have not been noted to 
manifest appreciable disturbances of health. Obviously, the de- 
tection of such carriers in localities where plague occurs or is 
suspected, is accomplished by the examination of considerable 
numbers of trapped or shot rats and squirrels. Bacillus pestis, 
ordinarily, can readily be demonstrated in the lesion bacteriologi- 
cally and through animal inoculation tests. 

Rodents carrying B. pestis in lesions such as above described, 
apparently are not a serious menace, and no special means have 
been employed for the control of such cases. However, in dis- 
tricts where plague has existed, the possibility of recurrence 
through such animals must be considered, and so far as rats are 
concerned, should serve as a stimulus for continued sanitation 
and measures contributing to the extermination of rats, even 
though an organized extermination campaign is not in progress. 

10. Bacterium tularense 

McCoy (16) in examining ground squirrels for evidence of 
plague, found lesions which could have readily been mistaken for 
those of that disease. Subsequently the causative organism was 
isolated by McCoy and Chapin (17) and named Bacterium tularense, 
they adopting such name because it was in squirrels from Tulare 
County, Calif., that the disease was first noted. 

Man is readily susceptible to infection with this organism either 
by insect bites or direct inoculation into abrasions. A local lesion 
is produced with glandular swellings and continued fever. The 
mortality is low. 

While lesions of the disease may be found in the spleen, liver, 
lungs and lymph glands, a number of squirrels were found harbor- 
ing the organism in a single bubo. Such animals are carriers in 



ORGANISMS PATHOGENIC FOR MAN AND ANIMALS 141 

the same sense as rodents harboring B. pestis in residual buboes. 
The infection has also been found in jack rabbits. 

Habitat of the organism. In those animals which may be classed 
as carriers, Bact. tularense is harbored in one or more buboes, 
the inguinal, pelvic, axillary and cervical glands being most 
frequently affected. McCoy states that these buboes in the 
squirrel are usually as large as a pea, sometimes larger. They are 
rather firm and when cut present a dry, yellowish, or blood-stained 
surface. Some hemorrhage is frequently found in the surrounding 
tissue. The gland structure is, as a rule, replaced by a firm, caseous 
mass. Purulent glands are uncommon. 

Detection and management. The organism can be definitely 
identified in affected glands through bacteriological means and 
animal inoculation tests. Bact. tularense is a very difficult 
organism to cultivate, the common types of media being unsuit- 
able for its growth. McCoy and Chapin found, however, that 
it could be cultivated on an egg medium made entirely of the 
yolk. The organism appears as a minute rod 0.3 to 0.7 micron 
in length and is frequently capsulated. It stains best with carbol- 
fuchsin or gentian violet. 

Little is known as to the importance of Tularemia in squirrels 
or rabbits and no special measures have been employed for its 
control. 

11. Bacillus erysipelatis suis 

Swine erysipelas, caused by Bacillus erysipelatis suis, is an 
important disease of swine in European countries. Recently, 
however, the disease, in a mild form, has been definitely recog- 
nized in the United States. It usually manifests itself as an acute 
septicemia with a characteristic reddening of areas of the skin. A 
mild, urticarial form ("diamond-skin disease") and a chronic 
type are also recognized. 

The carrier problem in swine erysipelas has been given con- 
siderable attention by European investigators and the fact 
definitely established that a large percentage of hogs in localities 
where the disease is prevalent, are carriers of the organism. 

Swine erysipelas occasionally occurs in man following infec- 
tion of skin injuries. In such cases there is an erysipelas-like 



142 CARRIERS IN INFECTIOUS DISEASES 

reddening of the skin accompanied by a swollen condition of the 
neighboring lymph glands. At times, the skin lesions assume a 
blackish-red color and exfoliation of the epidermis occurs with 
exudation of serum. Swelling of joints in the region of such lesions 
may also be noted. Infection through ingestion of the organism 
either does not occur, or is extremely rare. Lubowsky (18) re- 
ports a case of jaundice and intestinal catarrh in a boy in whose 
feces he found large numbers of bacteria identical with B. ery- 
sipelatis suis. This may possibly have been a case due to infection 
through the alimentary tract although there was no definite proof 
of same. In man the disease usually terminates in recovery after 
3 or 4 weeks. It may, however, persist for two or three months. 

Habitat of the organism. The bacillus of swine erysipelas is 
frequently found in large numbers in the crypts of the tonsils of 
carriers. No lesions other than an occasional slight inflammatory 
process have been noted in such carriers. 

In the intestines the organism is very frequently found in 
mucous plugs of the ileo-cecal valve. Olt (19), who has contrib- 
uted considerably to our knowledge of carriers in swine erysipe- 
las, frequently noted the bacillus in minor intestinal lesions caused 
originally by parasites, especially Strongyli. 

Out of 50 apparently normal animals examined, Pitt (20) found 
28 or 56 per cent harboring the erysipelas organism in their tonsils. 
In an examination of the intestines of 66 animals he found Bacillus 
erysipelatis suis in 26 or over 43 per cent of those examined. 

Detection and management. Because of the large percentage 
of carriers in districts where the disease exists and the difficulty 
which is experienced in obtaining satisfactory specimens of 
tonsil secretions for bacteriological examination, routine examina- 
tions for the detection of carriers is ordinarily impracticable in 
such localities. In special cases, however, where valuable breed- 
ing animals are being introduced into territory free of swine 
erysipelas, bacteriological examinations should be made of "swab- 
bings" from the throats of such animals during their quarantine 
period. 

Examination of the feces can be carried out without difficulty, 
and in some cases will yield positive results where the bacillus is 
carried in the intestinal tract. However, as the organism is 



ORGANISMS PATHOGENIC FOR MAN AND ANIMALS 143 

eliminated only sporadically from the intestines, a single negative 
bacteriological finding, obviously, would not indicate that the 
animal was not a carrier. 

The problem in those localities where the disease exists resolves 
itself into one of immunizing susceptible animals. Fortunately, 
good results can be obtained through vaccination against the 
disease. The method of Pasteur, giving two injections, twelve 
days apart, of a culture which has been attenuated by passage 
through rabbits, may be used, or the method of Lorenz and 
Leclainche, in which immune serum and virulent culture are 
administered simultaneously and followed in 12 days by an injec- 
tion of culture alone, may be employed. 

Cases of the disease in man have been confined to persons 
working around hogs in localities where swine erysipelas exists, 
and then only after minor skin injuries. Possible transmission of 
the disease to man from carriers can, therefore, be largely con- 
trolled through proper attention to tissue injuries. 

12. Miscellaneous facultative-pathogenic bacteria 

In addition to the various organisms of specific diseases already 
enumerated, animals are known to harbor in their upper air 
passages, intestines, genital tracts, and in the case of milch 
animals, in their udders, a considerable variety of pyogenic and 
facultative-pathogenic organisms. Under suitable conditions, in 
the body of their host, or in other animals or man directly or 
indirectly infected by such carriers, these bacteria are often cap- 
able of setting up various pathological processes. Included in 
this category are various types of streptococci, staphylococci, 
virulent strains of Bacillus coli, Bacillus pyocyaneus, Bacillus 
pyogenes, Bacillus botulinus, Bacillus aerogenes capsulatus, etc. 

Habitat of the organism. Streptococci, Staphylococcus albus, 
aureus and citreus, and Bacillus pyocyaneus are among those 
organisms frequently found in the upper air passages of horses, 
cattle, sheep, swine, dogs, cats, etc. 

Bacillus pyogenes, an organism which, under favorable condi- 
tions, is occasionally responsible for suppurative processes in the 
lungs, pleurae, peritoneum, etc., of hogs, arthritis in hogs and 
cattle, and inflammatory processes of the udder of cows, goats 



144 CARRIERS IN INFECTIOUS DISEASES 

and sheep, is frequently found in large numbers in the grayish, 
mushy plugs in the crypts of tonsils of healthy hogs. 

Of the large variety of bacteria found in the intestines of horses, 
cattle, sheep, swine, etc., which have not been previously men- 
tioned, and which may prove pathogenic under particular condi- 
tions, are virulent types of Bacillus coli, Bacillus lactis aerogenes, 
Bacillus proteus mirabilis, Bacillus pyocyaneus, Bacillus botu- 
linus and Bacillus aerogenes capsulatus. 

Virulent strains of Bacillus coli communis, Bacillus lactis 
aerogenes, Bacillus proteus mirabilis and Bacillus pyocyaneus, are 
frequently found as factors in cases of so-called "white scours'* 
of sucklings, especially calves. 

Bacillus botulinus is occasionally found in the intestinal tract 
of normal hogs. Such carriers are of importance because of the 
possible contamination of foodstuffs with particles of fecal matter 
from hogs. 

Bacillus aerogenes capsulatus is frequently found in the intes- 
tinal tracts of healthy herbivora. This organism has not been 
incriminated as a cause of natural infection in animals, but is of 
importance as a factor in the infection of extensive wounds in 
man, especially war wounds. 

Besides those organisms heretofore referred to as being harbored 
in the udders of cows and goats, Bacillus pyogenes, Bacillus 
phegmasis uberis, and various types of staphylococci, have been 
found in the udders of apparently healthy animals. These 
organisms are capable, under favorable conditions of producing 
inflammatory and purulent processes in the udders of animals, 
and under certain circumstances, may possibly prove pathogenic 
for man. 

Detection and management. The organisms referred to in the 
foregoing paragraphs can practically all be readily detected in 
carriers through the employment of bacteriological methods 
usually utilized for the identification of the different members of 
this group, without difficulty. 

Because they are chiefly facultative-pathogenic organisms and 
with one or two exceptions, are widely distributed, but little 
attention has been given to carriers of these bacteria. 



ORGANISMS PATHOGENIC FOR MAN AND ANIMALS 145 

B. CARRIERS OF PROTOZOA 

1. Leishmania canis 

In several localities where infantile Leishmaniasis, a tropical, 
febrile splenomengaly, or kala-azar of young children is prevalent, 
Leishmania canis, an organism indistinguishable from Leishmania 
infantum, has been frequently found in dogs. There are also 
rare instances of its occurrence in cats. Sergent, Lombard and 
QuiHchina (21) found Leishmania in the bone marrow of a cat. 
The organism has been demonstrated in dogs in Tunis, Algeria, 
Italy, Sicily, Spain, Greece, Malta and Transcaucasia. The 
disease in canines is usually of a very benign character although 
some animals may show marked disturbances of health as a result 
of the infection. Frequently, however, Leishmania canis is 
harbored in the bodies of dogs showing no appreciable evidence 
of disease whatever. 

There is considerable evidence tending to show that the parasite 
of Leishmaniasis can be transmitted from animal to animal by 
fleas. The probability therefore exists that carriers of the organ- 
ism among dogs may prove a source of infection for man. 

Habitat of the organism. The Leishmania harbored by dogs 
may be found in the endothelial cells of the spleen and liver, in the 
myelocytes and rarely in the leucocytes of the peripheral blood. 
In such cells they appear as numerous oval bodies 2 to 4 microns in 
length and 1.5 to 2 microns broad. Each organism contains a 
large nucleus and a smaller blepharoplast. Stained by Giemsa's 
method the large nucleus appears as a pale red body whereas the 
smaller blepharoplast stains a dark violet. 

Detection and management. Very rarely an occasional poly- 
morphonuclear or mononuclear leucocyte of the peripheral blood 
may be found to contain the parasite. Thus, in some few instances, 
careful examination of a number of blood preparations may prove 
successful in demonstrating the organism in carriers. Negative 
findings, however, are without significance. 

Microscopic examination of material obtained by puncture of 
the spleen or liver is the only method giving promise of success in 
the majority of cases of actual carriers of Leishmania. In making 
the puncture, a fine, scrupulously clean, hypodermic needle attached 



146 CARRIERS IN INFECTIOUS DISEASES 

to a syringe by means of a small piece of rubber tubing, is em- 
ployed. It is important that the needle be absolutely dry as a 
trace of water will distort or burst the parasite, making its rec- 
ognition exceedingly difficult or impossible. 

In the dog the dorsal end of the spleen does not vary in position. 
The position of the rest of the organ, however, is very variable. 
The dorsal portion of the spleen lies ventral to the vertebral end 
of the last rib and the first lumbar transverse process, on the left 
side of the body. The preferable point of penetration, therefore, 
is just posterior to the last rib close to the transverse process of 
the first lumbar vertebrae. In making a liver puncture a point 
close to the anterior border of the right twelfth rib, about two- 
thirds of the distance between the vertebral extremity and costo- 
chondral junction of this rib, is the best point of entry for the 
needle. When the puncture is made the animal should be well 
restrained in order to guard against tearing the organ through 
sudden movement. 

It is not necessary to obtain blood from the organ to insure 
results, a small amount of the spleen or liver pulp being most 
desirable. On withdrawing the needle the material is blown out 
on a clean cover slip, allowed to dry, stained by Giemsa's or 
Leishman's methods, and examined microscopically for Leish- 
mania. 

Until recently, medical treatment of Leishmaniasis offered but 
little hope of success. Lately, however, in human medicine, good 
results have been obtained from intravenous injections of tartar 
emetic, extending the treatment over a period of several months, 
gradually increasing the dosage. While in exceptional cases 
attempts to rid dogs of the parasite by medicinal means might be 
justified, generally, animals proven to be carriers of Leishmania 
should be promptly destroyed. 

As fleas are likely factors in the transmission of the infection, 
dogs and cats in localities where the disease is prevalent should be 
kept as free as possible from fleas. 



ORGANISMS PATHOGENIC FOR MAN AND ANIMALS 147 

C. CARRIERS OE FILTERABLE VIRUSES 

1. The virus of foot-and-mouth disease 

Foot-and-mouth disease or aphthous fever, caused by an ultra- 
microscopic, filterable virus, which up to the present time has not 
been artificially cultivated, is an important disease of cattle and 
other cloven-footed animals. The disease is prevalent in Europe, 
Asia, Africa and South America. At present it does not exist in 
the United States, the last and largest outbreak having occurred 
here in 1914-1915. 

Loeffier, Hess, Zschokke, Bartolucci, Neverman and various 
other investigators have shown that cattle which have had foot- 
and-mouth disease often harbor the virus and are capable of in- 
fecting other animals for considerable periods following recovery. 
Just how long such animals may remain carriers has not been 
definitely ascertained. Cases are on record, however, in which 
it has been definitely demonstrated that some carriers are capable 
of spreading the infection 7 months after recovery from the 
disease. 

Man not infrequently contracts foot-and-mouth disease. The 
infection is usually brought about through the ingestion of raw 
milk or cheese and butter prepared from milk containing the 
virus. Infrequently infection may occur as a result of direct 
contact with affected animals. 

The disease in man commences with a slight fever, with nausea 
in some cases. The buccal mucous membranes become inflamed 
and vesicles, sometimes as large as peas, develop, especially on 
the lips, gums and cheeks. Vesicles may occasionally develop 
on the conjunctivae. Exanthema of the skin of the hands, par- 
ticularly at the end of the fingers and at the base of the nails, 
occurs. Headaches, dullness, dizziness, abdominal cramps and 
diarrhea may be observed. The disease in adults usually runs a 
mild course. In children a severe gastro-intestinal catarrah is 
occasionally associated with the disease and may lead to fatal 
terminations. 

Bussenius and Siegel (22) in recording 16 outbreaks of foot-and- 
mouth disease among animals, occurring between 1878 and 1896, 
report that entire families, and in several instances the great per- 



148 CARRIERS IN INFECTIOUS DISEASES 

centage of persons in certain townships, became affected with the 
disease. A total of 75 cases terminated fatally. 

Thus, while the disease may be transmitted to the human 
species from animals suffering from the disease, until more definite 
knowledge is gained as to the various possible locations of the 
virus in the body of recovered animals which harbor the same, 
it will be impossible to state just how much of a menace carriers 
are to the health of man. 

Habitat of the virus. As above indicated, studies of the carrier 
problem in foot-and-mouth disease, unfortunately, have not as yet 
established with certainty all possible places of abode of the 
filterable virus in the animal body. 

Zschokke (23) demonstrated that vesicles, such as occur in the 
interdigital space, the plantar cushion and coronary band, may 
likewise be found between the horn and sensitive lamina of the 
hoof. Such vesicles may become confluent with the vesicles of 
the interdigital space or plantar cushion, thus opening to the out- 
side, or they may remain separate. In the latter event the virus 
contained in the vesicles remains in such location long after the 
animal has recovered, and is brought to the surface by the natural 
wearing away of the hoof. The spread of foot-and-mouth disease 
by a carrier thus harboring the virus in the hoof, has also been 
reported by Bang (24). 

It does not follow, of course, that the virus of foot-and-mouth 
disease is always localized in the hoofs of carriers. That it is 
probably harbored in other parts of the body and at times elimi- 
nated with the urine, feces, milk or saliva, is evident from the 
history of numerous outbreaks of the disease following the intro- 
duction of recovered animals into herds free of the infection. 

Detection and management. Loefner (25) , in concluding his report 
on carriers of the virus of foot-and-mouth disease, stated that at 
that time there was no method known to distinguish virus carriers. 
The handicap resulting from inability to utilize bacteriological 
methods in the study of such carriers is, of course, obvious. 

During the 1914-1915 outbreak of aphthous fever in the United 
States, the Bureau of Animal Industry of the United States 
Department of Agriculture (26) before releasing from quarantine 
the National Dairy Show Herd, the only herd of cattle affected 



ORGANISMS PATHOGENIC FOR MAN AND ANIMALS 149 

with the disease which was not destroyed, was confronted with 
the problem of definitely ascertaining whether or not any of these 
recovered animals were carriers of the virus. The disease had 
been eradicated from this country and a single carrier could, of 
course, have started the infection anew. 

The recovered animals were maintained under the most rigid 
type of quarantine. A number of healthy young cattle, ranging 
from one to one and one-half years of age, were placed in contact 
with the recovered animals and were further subjected to various 
inoculation tests. In the exposure tests a susceptible animal 
was placed between two recovered animals and allowed to remain 
there forty-eight to sixty-four hours, after which time it was 
placed between two other recovered animals. This procedure 
was carried out until all recovered animals had been given an 
opportunity to infect the susceptible animals. The susceptible 
animals were rotated in this way three times so that each test ani- 
mal was exposed at least one hundred and forty-four hours to each 
recovered case. In the meantime the recovered animals had been 
divided into groups and specimens of saliva, urine, vaginal dis- 
charge, watery extract of feces, scrapings from the interdigital 
spaces, and milk from each group were inoculated into the buccal 
cavity of the susceptible animals by rubbing the membranes 
briskly with a piece of gauze saturated with such specimens. 
Further, towards the end of the quarantine period a number of 
hogs were allowed to consume such leavings and droppings from 
the recovered cattle as had been permitted to remain, and were also 
fed milk from the cows. 

These tests were continued over a period of seven months when 
the quarantine was lifted. They indicated that there were no 
carriers, capable of transmitting the disease, in this particular 
herd of recovered animals, which finding was subconsequentially 
borne out through failure of the released animals to infect others. 

Numerous inoculation and exposure tests, as above outlined, 
to determine whether or not animals are carriers of the virus of 
foot-and-mouth disease, obviously, would not be practicable with 
individual animals, except in cases of breeding stock of consider- 
able value. 



150 CARRIERS IN INFECTIOUS DISEASES 

As previously indicated, foot-and-mouth disease does not now 
exist in the United States and in the outbreaks that have occurred 
all infected herds, with the exception of the single instance noted, 
were promptly destroyed. Thus, in this country we have no 
carrier problem. However, in those localities where the disease 
exists, sanitary and quarantine measures must be relied on to 
minimize the spread of the infection by carriers. 

With a view to eliminating all possibility of tranmission of the 
disease to man, through milk from cows which have recovered 
from the disease, the same should be properly pasteurized. 



CHAPTER XVIII 

Carriers of Organisms Pathogenic for Animals and 
Possibly for Man 

a. carriers of bacteria 

1. Streptococcus of infectious mastitis of cattle 

Milch cows frequently suffer from mastitis as a result of in- 
fection with any one of a variety of bacteria. A streptococcus of 
the pyogenes type, however, is generally responsible for that form 
of the disease which is transmitted from animal to animal. Kitt, 
describing a streptococcus of bovine mastitis, referred to it as 
"Streptococcus agalactiae." 

Cows which have apparently recovered from mastitis, and in 
some instances, cows with no history of having had the disease, 
often harbor streptococci in their udders for long periods of time. 

Habitat of the organism. The udder may harbor and eliminate 
streptococci for several years. In those cases which have ap- 
parently not suffered an attack of mastitis, autopsy, as a rule, 
reveals no demonstrable changes in the udder tissue except, occa- 
sionally, a slight catarrhal thickening of the epithelium of the milk 
ducts. In cases with a history of having had the disease, however, 
remaining evidence of the attack is usually present in the form of 
fibrous tissue changes of varying degree, with atrophy of the 
alveolar structure of the parenchyma of the udder. A thickened 
condition of the epithelial lining of the milk ducts, from which 
the streptococcus may usually be isolated, is also a common 
finding in such carriers. 

There has been considerable disagreement among various in- 
vestigators as to the pathogenicity of streptococci of bovine origin 
for man. Some are of the opinion that man is readily susceptible 
to infection with bovine streptococci transmitted through milk 
from infected animals. The weight of evidence, however, stands 
in refutation of such conclusion. Generally, man possesses con- 

151 



152 CARRIERS IN INFECTIOUS DISEASES 

siderable immunity to streptococci of bovine origin. Undoubt- 
edly, however, streptococci of human origin occasionally gain en- 
trance into the udder of cows through infected milkers, multiply 
in the glands, and may or may not set up pathological processes. 
Milk containing such organisms, is obviously dangerous as food 
for man unless pasteurized. 

Detection and management. The organism can usually be iso- 
lated from the milk of carriers, by ordinary bacteriological 
methods, without difficulty. After the udder has been thoroughly 
washed with soap and water, followed by a 1:1000 solution of 
bichloride of mercury, and the operator's hands disinfected, the 
specimen of milk should be drawn direct into sterile containers 
and cultured with the least practical delay, icing the specimen if 
there will be appreciable loss of time in getting the same to the 
laboratory. 

Our lack of accurate means for the definite identification of 
different types of streptococci applies, of course, in the case of the 
organism occurring in mastitis. The mastitis streptococcus must, 
however, be differentiated from Streptococcus lactis found nor- 
mally in milk. Streptococcus lactis is characterized by its short 
chains of 3 or 4 organisms, some cells appearing elongated with 
tapering ends. When grown in litmus milk the color reduction 
precedes curdling and is complete. The mastitis streptococcus 
grows in long chains, and in litmus milk, causes curdling which 
may be followed by an incomplete reduction of the litmus. 

The streptococcus usually enters the udder through the milk 
ducts, thus the transmission of the infection from the carrier to 
healthy cows is accomplished chiefly by the hands of the milker. 
Spread of the disease by this means can be controlled by requiring 
the milker to disinfect his hands after milking a known or sus- 
pected carrier. 

Attempts have been made to eliminate the streptococcus from 
the udders of carriers through the injection of mild antiseptic 
solutions (10 per cent solution of argyrol, etc;) but the results, 
while worthy of trial, are not uniformly successful. Autogenous 
bacterins have also been employed with variable results. 

A number of carriers of the organism suffer recurrences of the 
disease. Such cows usually develop marked udder changes with 



OEGANISMS PATHOGENIC FOR ANIMALS AND MAN 153 

great impairment of the functional activity of the gland. Thus, 
in addition to being carriers of the infection, they are a loss as 
milch cows, and unless they have a distinct breeding value, should 
be "beefed." Milk from herds in which there are known carriers 
of streptococci capable of producing mastitis in cows, should be 
pasteurized, in order to eliminate all chance of it proving detri- 
mental to the health of man. 

2. Bacterium abortus (Bang) 

Of all infectious diseases of animals, bovine infectious abortion, 
caused by Bacterium abortus (Bang), is probably without an equal 
in importance from the standpoint of carriers. When it is 
realized that from an economic standpoint infectious abortion of 
cattle in the United States is second only to tuberculosis, and that 
carriers are very potent factors in its spread, their importance 
cannot be over-rated. According to Schroeder (27) 60 per cent 
of all infected cows at some time harbor Bacterium abortus in 
their udders. 

While up to the present time this organism has never been 
definitely demonstrated to be pathogenic for man, nevertheless, 
it is possible that in specific instances and under certain conditions, 
this bacterium which is capable of producing marked lesions of a 
grave nature in various experimental animals, may prove det- 
rimental to human beings consuming milk from carriers of the 
organism. 

Mohler and Traum (28) inoculated emulsions of 56 tonsils and 
adenoids from children into guinea pigs and produced lesions in 
the liver, spleen and testicles in one of the inoculated pigs. Bac- 
terium abortus was recovered from these lesions. Larsen and 
Sedgwick (29) submitted blood specimens from 425 children to 
the complement-fixation test for Bacterium abortus infection and 
obtained 73 positive reactions. Later work by these investigators 
with blood serum from 42 new-born babies who had not received 
cows' milk resulted in negative reaction to the serological test. 
Larsen and Sedgwick indicated that these reactions might possibly 
be due to a passive immunity resulting from the ingestion of milk 
containing antibodies. Later work along this line by Cooledge 



154 CARRIERS IN INFECTIOUS DISEASES 

(30) tends to indicate that these reactions are generally due to the 
absorption of antibodies contained in infected milk. 

Habitat of the organism. Bacterium abortus has a particular 
affinity for embryonic tissue, its natural habitat being the epithe- 
lium of the chorion. In infected cows it is practically always 
found in the uterus during pregnancy, even though the animal 
goes through the full period of gestation and has an apparently 
normal parturition. After parturition, however, the organism 
soon disappears from the uterus; usually within several weeks. 
In exceptional cases it may persist for one and one-half to two 
months. 

In the absence of embryonic tissue Bacterium abortus finds the 
udder a suitable place to maintain its existence. Thus in a large 
percentage of infected cows the abortion organism is harbored 
in one or more quarters of the udder and may be eliminated with 
the milk for periods varying from a few weeks to six or seven years. 
Up to the present time it has not been established that udder 
lesions, definitely attributable to Bacterium abortus, occur in 
cows carrying the organism. 

The organism remains localized in the udder during the non- 
pregnant state in the cow but readily invades the uterus through 
the blood stream during pregnancy. Thus, the udder, in addition 
to eliminating the infection to the outside more or less continu- 
ously, constitutes a focal source of infection from which the uterus 
of its host may be reinfected when conditions there are favorable. 

In addition to the cow, the bull may harbor and eliminate 
Bacterium abortus with his seminal fluid. Buck, Creech and 
Ladson (31) in an examination of 325 mature bulls, isolated 
Bacterium abortus from the vesiculse seminalis in four instances. 
The organism in the bull apparently shows predilection for the 
seminal vesicles although it has been found in other parts of the 
reproductive organs. 

Detection and management. In the detection of carriers of 
Bacterium abortus among cows and bulls, the agglutination or 
complement-fixation test should be resorted to, and this followed, 
in the case of cows, by bacteriological examinations of the milk 
from each quarter of the udder. In bulls, when practicable to 
obtain specimens of the seminal fluid, the same should likewise be 



ORGANISMS PATHOGENIC FOR ANIMALS AND MAN 155 

subjected to bacteriological examination. Because of its relative 
simplicity, the agglutination test is the preferable of the serological 
tests. In reliability for this work, it compares favorably with the 
complement-fixation test. 

In applying the agglutination test either blood or milk serum 
from the suspected animal may be used. Blood serum, however, 
is preferable because in positive cases it usually possesses a greater 
number of agglutinins. In interpreting the agglutination test 
the lowest dilution in which agglutination is obtained which should 
be considered positive, has not been definitely settled. Agglutina- 
tion in a dilution of 1 to 50 or greater, however, should be taken 
to indicate that the animal is then, or was at some time previously, 
infected with Bacterium abortus. If positive reactions are ob- 
tained with serum in dilutions of 1 to 50 or greater but in less than 
1:200, the animals should be isolated and the agglutination test 
repeated after three week intervals. Declining reactions in di- 
lutions below 1:200 can be taken, with a reasonable degree of 
certainty, to indicate that the animal is not a disseminator of 
Bacterium abortus. Schroeder (27) in speaking of the work of 
the United States Bureau of Animal Industry and other investi- 
gators with the agglutination test for infectious abortion, states 
that where it can be proven that a cow harbors Bacterium abortus 
in her udder, the agglutination reaction obtained with blood or 
milk serum will be positive in a dilution of 1 :200 or more. 

In the bacteriological examination of milk to detect carriers of 
Bacterium abortus, Huddleson (32) recommends a liver infusion 
agar, prepared without excessive heating and filtered through 
glass wool rather than cotton or paper, and with a H-ion concen- 
tration between 6.6 and 6.4. One part of a saturated aqueous solu- 
tion of gentian violet to 10,000 parts of this medium will inhibit 
the growth of a large percentage of organisms other than Bacterium 
abortus. The inoculated plates should be incubated at 37.5°C. 
in air-tight containers in which approximately 10 per cent of the 
air has been replaced by C0 2 gas, an increased carbon dioxide 
tension being essential to the initial growth of Bacterium abortus. 

Cows and bulls demonstrated to be carriers of Bacterium abortus 
should not be introduced into uninfected herds. The ideal method 
of control, would, of course, be the slaughter of all cattle reacting 



156 CARRIERS IN INFECTIOUS DISEASES 

to the agglutination test followed by thorough disinfection of the 
premises and subsequent ret est s of remaining animals. In herds 
of pure-bred animals, or where the infection is limited and of 
recent introduction, such method might be most economic. 

While this radical method might prove the most economic 
procedure in some instances, generally, in herds where the disease 
is well established, and in which there is a high percentage of 
carriers, it would not be feasible. The situation in such cases 
can probably best be handled by maintaining the herd intact 
without introducing new animals into it and without per- 
mitting animals from it to be introduced into other herds. Thus, 
while carriers in such herds will not be eliminated they are among 
animals which have developed more or less immunity to the 
infection and consequently are in the place where they will do the 
least harm, especially where energetic sanitary measures are 
employed with a view to preventing mass infection. 

The bull, known to harbor and eliminate Bacterium abortus, 
under average conditions apparently does not infect healthy cows 
through the vagina. Infection from such animal is usually 
brought about through the ingestion of food or water contami- 
nated with semen dripping from the penis of the bull or which has 
escaped from the vagina of the cow subsequent to service. Thus 
where such carriers are utilized for breeding purposes, precautions 
should be taken to prevent the spread of the infection in this 
manner. On the other hand, it appears possible that under certain 
unusual conditions, especially in cases of slight injury occurring 
during service, cows may become infected through the vagina 
when served by bulls known to carry and eliminate the organism. 
It cannot, therefore, be definitely stated that such carriers are 
invariably safe for breeding purposes. 

Although possible pathogenicity of Bacterium abortus for man 
has not been established, pasteurization of milk from herds in 
which there are carriers is fully warranted. 

B. CARRIERS OF PROTOZOA 

1. Trypanosomes 

There are several important diseases of domestic animals, 
known to be due to trypanosomes. Further, a very large variety 



ORGANISMS PATHOGENIC FOR ANIMALS AND MAN 157 

of trypanosomes of little or no established pathogenicity have 
been noted in numerous species of lower animals. 

Of the more important diseases of animals due to trypanosomes 
there are four which are outstanding. Nagana, an acute or 
chronic affection of solipeds, cattle, sheep, goats and other 
ruminants, caused by Trypanosoma Brucei, at present exists in 
Southeast Africa. The disease is characterized by remittent fever, 
subcutaneous edema, marked anemia and emaciation. It is 
transmitted by the tsetse fly. 

Surra, designates those trypanosomiases of domestic animals 
caused by Trypanosoma Evansi. The disease causes great losses 
among solipeds and camels. Cattle and dogs are less severely 
affected. Surra occurs in India, Persia, China, the Philippines, 
Sumatra, Java, Mauritius, and apparently in northeastern Africa. 
Its manifestations are in a general way similar to those of nagana. 
Tropical flies, especially Tabanus tropicus and Tabanus lineola, 
are transmitting agents of the disease. 

Dourine, caused by Trypanosoma equiperdum, is a chronic 
disease of horses, characterized by inflammatory swelling of the 
external genitals with subsequent symptoms of paralysis. The 
disease at present appears to exist in Spain, Russia, Africa, Persia, 
India, Java, Roumania, France and in several states in the United 
States. Characteristic of dourine is the fact that the natural 
mode of infection is through coitus. 

Mai de caderas, caused by Trypanosoma equinum, is a fatal 
subacute or chronic disease of horses in South America, charac- 
terized by a paralysis of the hind quarters. Definite information 
is lacking as to the natural mode of infection. It is believed, 
however, that flies are capable of transmitting the disease. 

There are numerous records of carriers of trypanosomes patho- 
genic for animals, especially Trypanosoma Brucei and Evansi. 
According to Laveran and Mesnil (33) a large variety of species, 
particularly wild ruminants, harbor Trypanosoma Brucei in their 
blood without suffering impairment of health. Hutyra and Marek 
(34) report buffaloes, antelopes, hyenas, zebras and quaggas as 
carriers of the organism, such animals themselves being refractory 
to the infection. 

In surra the bovine species is much more resistant to the disease 
than equines. However, cattle and zebus in localities where the 



158 CAKRIERS IN INFECTIOUS DISEASES 

disease exists are very frequently carriers of the trypanosome. 
Such animals may harbor the organism for years without mani- 
festing disturbances of health. Camels which have recovered from 
surra frequently harbor Trypanosoma Evansi in their blood for 
long periods of time. In India the buffalo has been demonstrated 
as a frequent carrier of the parasite. Various wild animals such 
as foxes, jackals, hyenas, etc., may carry the organism. 

In dourine animals which have made an apparent recovery may 
continue to harbor the parasite in their bodies for a considerable 
period of time as is evidenced by relapses which frequently occur 
in such animals. 

Nothing definite is known regarding carriers in Mai de caderas. 

It has not been definitely established that trypanosomes patho- 
genic for man are, under natural conditions, carried by lower 
animals. However, Trypanosoma gambiense, the causative 
agent of so-called "sleeping sickness" in man has been experi- 
mentally demonstrated to be pathogenic for various species of 
animals, horses, cattle, sheep, monkeys, dogs, cats, rats and mice 
having been successfully infected. 

Bruce (35) and his co-workers were able to transmit Trypano- 
soma gambiense from infected monkeys to cattle by the bite of 
Glossina palpalis. They expressed the opinion that cattle may 
harbor the parasite. Thomas and Brienl (36) inoculated a cow 
with Trypanosoma gambiense and noted that it suffered a slight 
disturbance of health but soon returned to normal. More than a 
year later the blood of this animal was still infectious for rats. 

Habitat of the organism. With the exception of Trypanosoma 
equiperdum, the trypanosomes above mentioned, when harbored 
by animals, are present more or less intermittently in the blood 
stream. At periods they undoubtedly inhabit various tissues and 
organs when they cannot be demonstrated in the circulating blood. 

In dourine the trypanosome can, only in the rarest instances, be 
demonstrated in the blood of animals harboring the organism 
within their bodies. Recurrence of symptoms of the disease and 
positive serological reactions constitute the evidence that such 
animals actually harbor the infection. 

Detection and management. Microscopic examination of blood 
preparations from animals suspected of harboring trypanosomes 



ORGANISMS PATHOGENIC FOR ANIMALS AND MAN 159 

may be resorted to with successful results in a number of positive 
cases. However, such examination frequently results in failure 
to demonstrate the parasite. Animal inoculation tests often give 
positive results where the microscopic examination fails. 

The complement-fixation test has proven of great value in the 
detection of dourine among horses in the United States, and the 
same test can be used to good advantage in the detection of car- 
riers of trypanosomes. However, the complement-fixation test 
will not differentiate the type of trypanosome, the phenomena 
being a group reaction. Thus, while carriers may be detected by 
the serological test, identification of the type of organism har- 
bored can only be accomplished where it is possible to demon- 
strate and definitely recognize the particular parasite microscopi- 
cally, or where the typical disease can be produced as a result of 
experimental inoculation of susceptible animals. 

When carriers of pathogenic trypanosomes are detected in 
localities where trypanosomiasis is not prevalent, their destruction 
should be accomplished. In districts where the disease is wide- 
spread, however, measures looking to the protection of animals 
from flies, must be chiefly relied upon to combat the carrier prob- 
lem. In cases of animals harboring the dourine trypanosome, 
the problem can be effectively handled by castrating stallions 
known to harbor the organism and prohibiting the breeding of 
infected mares, or destroying the latter in countries where efforts 
are being made to eradicate the disease. 

2. Other protozoal and metazoal infections 

There is evidence tending to indicate that different species of 
animals may occasionally carry in their intestinal tracts various 
rhizopoda, ciliata, flageliata and sporozoa, in small numbers 
without manifesting disturbances of health. Again, it is possible 
that certain of such parasites may be harbored in rather large 
numbers by a particular species without detrimental results, 
whereas the same organism gaining entrance into the body of 
other species, including man, may cause marked disturbances. 
At the present time, however, there is very little known regarding 
carriers of this type. 



160 CARRIERS IN INFECTIOUS DISEASES 

Eichhorn and Gallagher (37), in reporting an outbreak of amebic 
dysentery among monkeys, point out the possibility of carriers 
occurring among such animals. The parasite in the cases de- 
scribed, however, apparently was not Endameba histolytica, the 
causative agent of amebic dysentery in man. 

Adult turkeys may harbor in their intestines Ameba melea- 
gridis, the etiological factor in infectious enterohepatitis ("Black- 
head") of turkeys. Apparently this parasite is also carried by 
chickens. There is no evidence that the organism is pathogenic 
for man. 

Balantidium coli is commonly found in the lower portion of 
the intestines of hogs. It is usually nonpathogenic for these 
animals but may occasionally produce a mild form of dysentery. 
This organism is capable of producing dysentery and ulceration of 
the intestines in man, occasionally setting up a process which 
terminates in death. 

Several types of trichomonas occur in swine and fowls. So 
far as is known, however, they are of but little importance. 

Various coccidia occur in cattle, sheep, dogs, cats, rabbits, 
fowls, etc. Undoubtedly there exists among such animals those 
which could be properly placed in the category of carriers. There 
is, however, but little information available on the subject. There 
are several cases on record where man has been infected with 
Coccidium cuniculi, the common coccidium of rabbits. 

In the same sense that carriers of protozoan organisms are 
recognized, carriers of various types of helminths exist among 
animals. Our knowledge of this phase of the carrier problem, 
however, is very meagre. 



CHAPTER XIX 

Carriers of Organisms Pathogenic for Lower Animals 

Only 

a. carriers of bacteria 
1. Bacillus bipolaris septicus 

Bacillus bipolaris septicus, various types of which make up the 
"Hemorrhagic Septicemia" or "Pasteurella" group and are known 
as B. bovisepticus, B. equisepticus, B. suisepticus, B. ovisepticus, 
B. avisepticus, etc., according to the species of animal from which 
isolated, is frequently harbored in the bodies of normal animals. 

According to Moore (38), upward of 80 per cent of normal cattle 
harbor in their upper air passages organisms corresponding in 
cultural characteristics, and in their effect upon rabbits, to Bacillus 
bipolaris septicus. Horses, swine, sheep, dogs, cats and fowls have 
also frequently been found as carriers of the organism. 

Fortunately, this bacillus is usually more or less of a facultative- 
pathogenic organism and only produces its specific disease when 
the normal resistance of the invaded animal is lowered or following 
a particular increase in its own virulence which sometimes occurs 
without apparent cause. 

Habitat of the organism. The favorite location of Bacillus 
bipolaris septicus in carriers apparently is the epithelium of the 
nasal cavity, larynx, pharynx and trachea. It is also found rela- 
tively frequent in the small and large intestines. 

Manninger (39) cites an experiment in which chickens were arti- 
ficially infected with the fowl cholera organism (B. avisepticus) 
and, while not developing the disease, eliminated the organism 
through their kidneys for months. He also cites an instance of 
a hen harboring highly virulent fowl cholera organisms in an old 
encapsulated abscess in the region of a joint in which she had a 
chronic arthritis. 

161 



162 CAREIERS IN INFECTIOUS DISEASES 

No tissue alterations, commonly found, and definitely attrib- 
utable to this organism when harbored by apparently normal 
animals, have been described. 

Detection and management. The organism can, as a rule, be 
readily cultivated from the upper air passages of carriers by ordi- 
nary bacteriological methods, and when carried in the intestinal 
tract, may likewise be isolated from the feces, but with less 
frequency. 

Because of the high percentage of carriers and the widespread 
distribution of organism of the Pasteurella group in nature, we 
are without means for ehminating them. Efforts, therefore, must 
be directed along sanitary lines with a view to maintaining the 
general health and resistance of animals, rather than endeavoring 
to eliminate the carriers. Further, vaccination against infection 
with organisms of this group, with properly prepared vaccines, is 
possibly of value. 

2. Bacillus necrophorus 

Bacillus necrophorus (Fliigge) under this and such additional 
names as "Bacillus diphtheriae vitulorum" (Loeffler), "Bacillus 
filif oralis" (Schutz), "Actinomyces cuniculi" (Gasperini), and 
"Streptothrix necrophora" (Kitt), since 1884 has been recognized 
as the causative factor of a variety of important pathological 
processes in domestic animals. The organism is widely distributed 
and is frequently harbored in the intestines of healthy herbivorous 
animals, especially hogs. There is no record of its having proved 
pathogenic for man. 

The principal pathological conditions for which bacillus necroph- 
orus is responsible includes gangrenous dermatitis of horses and 
mules, the so-called "foot-rot" and "lip-and-leg ulceration" of 
sheep, necrotic stomatitis of cattle, and multiple necrotic foci 
in the liver of cattle and hogs. The organism is also found as a 
secondary factor in various other diseases and conditions. Its 
lesions are characterized by a coagulation necrosis with subsequent 
caseation. 

In the United States Army during the world war, gangrenous 
dermatitis of horses and mules proved to be the second most 
important disease of animals in the United States. During the 



ORGANISMS PATHOGENIC FOR LOWER ANIMALS ONLY 163 

six month period July to December, 1918, 4036 cases of the disease 
were reported. Of this total 212 cases died or had to be destroyed 
on account of the disease. Of all deaths, from all causes, among 
all Army animals in the United States, for this period 6.41 per cent 
were due to gangrenous dermatitis. The weekly sick report during 
this period showed a ratio of over 275 animals per 1000 on sick 
report as a result of Bacillus necrophorus infection. 

Where a considerable number of animals are kept together in 
corrals, pens, lots, etc., which are wet and muddy, or contain 
large accumulations of manure, the infection spreads rapidly 
when once introduced. The importance of carriers when placed 
among animals in such surroundings is obvious. 

Habitat of the organism. Carriers of Bacillus necrophorus 
harbor the organism in their intestinal tracts, usually without 
manifesting appreciable lesions However, in hogs which have had 
the chronic form of hog cholera, Bacillus necrophorus is frequently 
found associated with Bacillus suipestifer in the intestinal ulcers 
described in the discussion of carriers of the Salmonella group 
(page 131). Further, the organism may be found in minor 
intestinal lesions originally due to parasites. 

Detection and management. The detection of Bacillus necroph- 
orus in carriers by bacteriological methods is by no means an 
easy undertaking. In the first place, carriers of this bacillus as a 
rule do not eliminate it in large numbers. Further, this organism 
is an extremely difficult anaerobe to isolate in pure culture. Char- 
acteristic of the organism is its beaded appearance in stained prep- 
arations. While it is distinctly a pleomorphic organism, it usually 
occurs as a long slender rod appearing more or less bent. Long 
filaments, measuring in some instances, over 100 microns in length, 
are frequently observed. 

The subcutaneous inoculation of rabbits with suspected material 
gives rise in positive cases to a hard inflammatory induration at 
the site of inoculation. After a few days the tissue in this area 
becomes caseous and necrotic, the rabbit usually dying within 10 
or 12 days. The necrotic tissue gives off a characteristic cheesy 
odor. In such lesions B. necrophorus can be demonstrated in 
large numbers. 



164 CARRIERS IN INFECTIOUS DISEASES 

Sanitary measures afford the chief means of preventing B. 
necrophorus infections. Well drained corrals, pens, etc., and 
proper disposal of manure and litter are potent factors in con- 
trolling the infection. 

3. Bacillus paratuberculosis 

Paratuberculous enteritis, or Johne's Disease, is a serious, 
chronic, infectious disease of the bovine species, characterized by 
a marked thickening and corrugation of the mucous membrane 
of the intestine. The etiological factor, Bacillus paratuberculosis, 
is an acid-fast organism closely resembling the tubercle bacillus. 

Young cattle are more resistant to the infection than adults, 
yet they are capable of carrying the infection for months or even 
several years, and therefore constitute an important carrier prob- 
lem. After maturity, a large percentage of such carriers them- 
selves become affected with the disease, especially following 
calving. 

While the disease in the vast number of cases runs a long chronic 
course and terminates fatally, there are, among adult cattle, 
occasionally cases of apparent recovery. Such animals invariably 
are active carriers of the infection, in some instances for periods 
of time extending over a number of months. Usually, however, 
they suffer recurrences which finally result in death. Such 
animals must be differentiated from the true immune carrier, as 
generally they are, in a strict sense, arrested cases, the carrier 
state existing during the period of inactivity. 

Habitat of the organism Carriers of the bacillus of paratuber- 
culous enteritis harbor the organism in the mucous membrane 
of the small and large intestine, the lower portion of the small 
intestine being a favorite location. 

In the case of young cattle which, while carrying the organism, 
have not suffered an attack of the disease, autopsy reveals little 
or no changes in the intestinal tract. Occasionally, however, 
small areas of the intestinal mucous membrane may appear 
thickened and slightly rugous. Sections from such areas show, 
principally, cellular infiltration and a swollen and more or less 
distorted condition of the villi. The organism can readily be 
demonstrated in such lesions. 



ORGANISMS PATHOGENIC FOR LOWER ANIMALS ONLY 165 

In carriers which have had the disease the mucous membrane of 
portions of the intestines appears, as a rule, greatly thickened and 
has a characteristic convoluted or corrugated appearance. Micro- 
scopic examination of sections of such tissue reveals a cellular 
infiltration, a marked distorted condition of the villi, and an 
increase of the interstitial tissue between the tubular glands in the 
glandular layer, with atrophy of the glands. In such sections the 
acid-fast bacillus can usually be demonstrated in considerable 
numbers. 

Detection and management. Microscopical examination of the 
feces from actual carriers often yield negative results. Repeated 
examinations of considerable quantities of the feces should, there- 
fore, be made. Further, the bacillus of Johne's disease must be 
differentiated from other acid-fast organisms. As it is non- 
pathogenic for the guinea pig, such experimental animal can be 
utilized in differentiating the organism from the tubercle bacillus. 
It must, however, still be differentiated from acid-fast organisms 
of a saprophytic nature. As it is exceedingly difficult to cultivate 
the Bacillus paratuberculosis, cultural methods, at present, offer 
but little aid. Hastings, Beach and Hadley (40) report fairly 
good results with a medium prepared by adding to filtered broth 
cultures of the human tubercle bacillus sterilized in the Arnold 
sterilizer for two hours, 15 grams of agar, 2 grams of beef extract, 
5 grams of peptone, 2.5 grams of potassium acid phosphate and 
24 cc. of glycerine, per liter of the filtered culture, adjusting the 
reaction to plus 1.5 to phenolphthalein. A small amount of sterile 
blood serum should be run over the surface of this medium just 
before inoculation. 

Bang (41) and several other investigators have called attention 
to the value of avian tuberculin for the diagnosis of paratuber- 
culous enteritis. Tuberculin prepared from the avian type of 
tubercle bacillus is utilized in order to eliminate the possibility of 
complications arising from reactions in tuberculous cows, animals 
infected with the bovine or human type of tubercle bacillus not 
reacting to avian tuber culin. Such tuber culin test may be used 
in the detection of carriers. 

A diagnostic agent ("Johnin") prepared similarly to tuberculin 
but from the specific organism of the disease has been made and 



166 CARRIERS IN INFECTIOUS DISEASES 

gives satisfactory results in diagnosing the infection. However, 
because of the difficulty encountered in propagating the bacillus 
it is but seldom that such agent can be obtained. 

As Johne's disease is fatal in the large percentage of cases, and 
as carriers, as a rule, eventually develop the disease, or if they 
have already had it, suffer recurrences which finally prove fatal, 
they should be slaughtered. 

4-. Bacterium pullorum 

The carrier problem in bacillary white diarrhea of young chicks, 
a disease due to an organism known as Bacterium pullorum, is 
without doubt the most important problem of its kind in the 
various infectious diseases of fowls. Gage (42), Jones (43), 
Rettger (44), and various other investigators, have definitely 
shown that the perpetuation of this disease is due, in a large 
measure, to carriers of the organism among adult hens, who may 
harbor the organism throughout their life. 

The organism is apparently non-pathogenic for man. This is a 
fortunate circumstance in view of the fact that the bacterium is 
frequently found in freshly laid eggs of carriers. 

Habitat of the organism. Carriers of Bacterium pullorum harbor 
the same in their ovaries. The changes in such ovaries are usually 
well marked. Examination of a normal ovary of the laying hen 
demonstrates a large mass of ova in various stages of development, 
some appearing as minute, colorless spheres, just visible to the 
naked eye, others being as large as a normal yolk and of a rich 
yellow color. The ovary which is infected with Bacterium pul- 
lorum, while possessing some apparently normal ova in various 
stages of development, will usually be found to contain a number 
of different sizes which appear as cysts. The smaller of such 
ova appear round or are slightly distorted. The larger are usually 
distorted so that they appear angular or flattened, and are of a 
mottled appearance, some lighter than normal, others of a dark, 
yellowish-brown color. In some cases the color is a peculiar dark- 
green, suggesting gangrene. The diseased ova contain a cheesy 
mass out of which may be expressed a clear amber-colored fluid. 
Bacterium pullorum may be readily isolated from such material. 



ORGANISMS PATHOGENIC FOR LOWER ANIMALS ONLY 167 

A large percentage of ova of hens with such ovaries never 
mature. However, such birds frequently lay fully developed eggs, 
capable of hatching, which contain the organism. In such cases 
the resulting chick has white diarrhea and infects others in the 
brood which may have been hatched from healthy eggs. Of those 
that survive a large percentage of the females are carriers, thus 
continuing the cycle of infection. 

Rettger, Kirkpatrick and Jones (44) in a series of experiments 
which they conducted found that over 25 per cent of female chicks 
infected with Bact. pullorum when small became permanent 
carriers of the infection. 

Detection and management. Jones (43) found that the macro- 
scopic agglutination test could be utilized to good advantage in 
detecting hens harboring Bact. pullorum in their ovaries. The 
value of this test has been confirmed by a number of other in- 
vestigators. 

In carrying out the agglutination test dilutions of 1 : 50, 1 : 100 
and 1:200 are made. In Jones' work serum from all infected 
fowls agglutinated in 1:50 and 1:100 dilutions, 91 per cent agglu- 
tinated in the 1 :200 dilutions and 82 per cent of 1 :500. Aggluti- 
nation in dilutions of 1 : 100 or more should be considered positive, 
in the 1:50 dilution, suspicious. 

Hens demonstrated to be carriers of Bact. pullorum should not 
be kept on premises where chickens are raised. Further, because of 
the diseased condition of the ovaries, such birds are not profitable 
layers. Therefore, their slaughter for food purposes is an econom- 
ical procedure. 

B. CARRIERS OF PROTOZOA 

1 . Piroplasma bigeminum and Piroplasma bovis 

In the southern part of the United States bovine piroplasmosis 
or Texas fever is an important disease of cattle. It is caused by 
Piroplasma bigeminum and is commonly transmitted by the tick 
Margarapus annulatus. European piroplasmosis (British "Red 
Water") is generally due to a smaller type of organism, Piroplasma 
bovis, and is usually transmitted by Ixodes ricinus. Clinically, 
Texas fever and European piroplasmosis of cattle are practically 



168 CARRIERS IN INFECTIOUS DISEASES 

indistinguishable. However, cattle immune to the Texas fever 
piroplasma are susceptible to the European type, thus clearly 
establishing that the two parasites are different species. 

Young cattle are quite resistant to piroplasma infection. Ani- 
mals raised in infected localities usually become immunized so that 
they do not suffer from severe attacks of the disease. Such 
animals, however, harbor the piroplasma and if introduced into 
districts where piroplasmosis does not exist, prove a source of 
infection for susceptible cattle if transmitting ticks are present. 

Piroplasma may persist for years in the blood of immune or 
recovered animals. Schroeder and Cotton (45) reported the case 
of a cow whose blood was infectious for over 10 years subsequent 
to her arrival at the United States Department of Agriculture 
Experiment Station from a Texas fever district in North Carolina. 

Habitat of the organism. Carriers of Piroplasma bigeminum and 
Piroplasma bovis harbor the same in their red blood corpuscles. 
Piroplasmosis is characterized by a marked diminution of red cells. 
After recovery, however, the number of red cells gradually ap- 
proach normal so that in carriers blood cell counts often demon- 
strate little or no diminution. 

Detection and management. The parasites of bovine piroplas- 
mosis may be demonstrated in the blood of carriers by micro- 
scopic examination. They are present, of course, in smaller 
numbers than are found in cases of the disease, consequently a 
more searching examination is often necessary. 

After shaving and cleaning an area of the ear of a suspected 
carrier a drop of blood should be obtained by making a small 
incision with a scalpel or lancet. A blood film should be prepared 
on a clean slide and stained for microscopic examination with 
Romanowski stain or one of its modifications. Piroplasma bigem- 
inum appear as pyriform organisms varying from 2.0 to 4.0 
microns in length and 1.5 to 2.0 microns broad, usually occurring 
in pairs in the red blood cells. They may be found side by side 
but frequently appear end to end on a parallel line or at an angle, 
the pointed ends being in opposition (dumb-bell forms) . In addi- 
tion to the pear-shaped forms, round, oval or pyramidal shapes 
may be noted. Occasionally but one parasite may be found in a 
cell while in other cells several pairs may be noted. Piroplasma 



ORGANISMS PATHOGENIC FOR LOWER ANIMALS ONLY 169 

bovis differs from Piroplasma bigeminum in that it is smaller and 
does not have the tendency to occur in distinct pear-shaped forms. 

As bovine piroplasmosis is transmitted from animal to animal 
by certain species of ticks, preventative measures, in the United 
States, have been reduced to quarantine of areas infected with the 
cattle tick and the inauguration of a well-organized campaign of 
tick eradication. Cattle from such districts cannot be shipped 
into uninfected territory except under certain restricted condi- 
tions. Between 1906 (the year eradication of the cattle tick was 
undertaken) and December 1921, 523,837 square miles of infected 
territory in the United States were freed of cattle ticks through 
systematic dipping of the cattle, reducing the infected area to 
206,015 square miles. 

In localities where bovine piroplasmosis is more or less wide- 
spread, and where quarantine and measures for the eradication of 
transmitting ticks are not employed, the immunization of sus- 
ceptible animals constitutes the only means of protecting cattle 
from infection coming from carriers. This is accomplished natu- 
rally in young animals brought up in infected districts. Suscep- 
tible adults may be immunized through the subcutaneous injec- 
tion of small amounts (5 cc.) of defibrinated blood of immunized 
or recovered cattle, preferably calves, in which the parasite occurs 
in small numbers. The inoculated animals should be kept in the 
stable for three or four weeks before being turned out to pasture. 
Eight to ten days after the inoculation the animals manifest 
symptoms of the disease which usually last from one to two weeks. 
Pregnant cows and animals in a state of impaired health should 
not be inoculated. 

Most inoculated animals survive the infection, although oc- 
casionally a few are lost. However, as the percentage of losses 
among non-inoculated animals, in localities where the disease is 
wide-spread, is considerably greater than that occurring in arti- 
ficially infected animals, the inoculation procedure is warranted. 

Where vaccination is employed to immunize susceptible ani- 
mals, we have, so far as the carrier problem goes, a unique situa- 
tion. The method employed to protect non-immunes against 
infection actually produces a large number of carriers. 



170 CARRIERS IN INFECTIOUS DISEASES 

2. Piroplasma caballi and Nuttallia equi 

Prior to 1910, Piroplasma caballi, Piroplasma equi or Babesia 
equi, as it has been variously termed, was the single etiological 
entity considered in connection with equine piroplasmosis. In 
1910, however, Nuttall and Strickland (46) reported the rosette 
or cross-form type of organism, which had previously been con- 
sidered merely a form of Piroplasma caballi, as a distinct and 
separate type of blood parasite and termed it "Nuttallia equi." 

At present the findings of Nuttall and Strickland are generally 
accepted and two types of organism recognized. However, as 
mixed infections are not of rare occurrence, and as it has been 
practically impossible to differentiate clinically the disease induced 
by these two types of organism, no attempt has been made to 
separate the two affections. Thus, the term "equine piroplas- 
mosis" includes those diseases caused by either one or both of the 
organisms mentioned. 

Equine piroplasmosis is of frequent occurrence in Russia, Italy, 
Africa and India. While it is not known to exist in the continental 
United States, it has been recognized on the Canal Zone. 

Horses which have recovered from the disease may harbor the 
organism in their blood for years and through the agency of ticks 
(the natural mode of infection) infect healthy animals. 

Habitat of the organism. Carriers of Piroplasma caballi and 
Nuttallia equi harbor the parasites in some of their red blood 
corpuscles. The number of red cells which may be found to con- 
tain the organisms, however, is exceedingly small as compared to 
that in actual cases of the disease. 

Detection and management. Carriers of Piroplasma caballi and 
Nuttallia equi may be detected through microscopic examination 
of stained blood-smear preparations from such animals. It is 
often necessary, however, to examine a large number of prepara- 
tions at different periods before the organism can be demonstrated. 

Piroplasma caballi represents the true type of Piroplasma and 
resembles, rather closely, Piroplasma bigeminum, the causative 
agent of Texas fever in cattle. It appears as a relatively large, 
elongated or pyriform body, averaging approximately 3 to 3.5 
microns in length and is usually found in the red blood cell in 
pairs or singly. 



ORGANISMS PATHOGENIC FOR LOWER ANIMALS ONLY 171 

Nuttallia equi is considerably smaller than Piroplasma caballi 
and is characterized by its occurrence in rosette or cross-forms, 
four parasites being thus grouped. Occasionally there may be 
observed small ring-like or coccus forms of the Nuttallia. 

At present there is no known medicinal agent which has given 
satisfactory results in eliminating these organisms from the blood 
stream. Thus, in countries or localities where equine piroplas- 
mosis has not become established the detection of a carrier of the 
infection would call for its immediate destruction. In communi- 
ties where the disease is prevalent, however, such procedure would 
not be feasible, especially when it is considered that a vast number 
of animals in such places are carriers of the organisms. In these 
localities only young native animals become affected, the older 
horses, mules and donkeys having more or less of an acquired 
immunity, develop the disease or suffer a relapse if they have 
previously had the affection, only under conditions which tend to 
lower their normal resistance. 

Susceptible animals should be kept from tick-infested pastures, 
especially during the warm months when ticks are numerous. 
The vaccination of susceptible animals according to the method 
recommended by Theiler demonstrated that passage of the or- 
ganism through donkey colts reduces the virulence of the para- 
site, especially for horses who are more susceptible to the disease 
than mules and donkeys. In carrying out the vaccination of 
susceptible animals, blood containing parasites which have been 
passed through 4 or more donkey colts, is used as the inoculum. 
Susceptible animals are injected with 1 cc. of such blood. Such 
inoculation gives rise to but a minor reaction. Pregnant mares 
and animals in poor condition should not be vaccinated. As in 
bovine piroplasmosis, vaccination actually produces a large num- 
ber of carriers. 

C. CARRIERS OF FILTERABLE VIRUSES 

1 . The virus of equine infectious anemia 

Equine infectious anemia, manifesting itself as an acute or 
chronic, septicemic affection with marked destruction of red blood 
corpuscles, is one of those diseases of horses caused by an ultra- 



172 CARRIERS IN INFECTIOUS DISEASES 

microscopic filterable virus, in which carriers are recognized. 
The malady is prevalent in several of the European countries, in 
Canada, and in the United States has been recognized in Minne- 
sota, South Dakota, Nebraska, Nevada, Kansas, New York, 
Virginia and Texas. It is undoubtedly more widespread than is 
generally believed. 

In practically all instances the disease eventually has a fatal 
termination. Animals which have the chronic form of the affec- 
tion sometimes make an apparent recovery, continuing in health 
for months or even years. Almost without exception, however, 
they suffer relapses which finally terminate fatally. Such ap- 
parently recovered horses are "relapsing carriers." They con- 
tinue to harbor the virus in their bodies and through its elimina- 
tion in the urine, are a menace to the health of other animals. 

Habitat of the virus. The virus of equine infectious anemia is 
present in the blood stream of carriers and is eliminated more or 
less continuously in the urine. 

The blood findings in infectious anemia vary with improvement 
of the animal, so that usually in carriers which have apparently 
recovered, the shortage of red corpuscles is very moderate as 
compared with the marked diminution (10 to 25 or even 50 per 
cent) of blood cells in active cases. 

Detection and management. Positive identification of carriers 
of the virus of infectious anemia can only be made through the 
inoculation of normal horses with blood specimens from sus- 
pected carriers. In positive cases a test horse given an intra- 
venous inoculation of 25 to 50 cc. of blood or blood serum (the 
particular amount apparently has no effect on the incubation 
period) usually develops the disease within eight or nine days, 
although in rare instances two or three weeks may elapse before 
the development of symptoms. In some cases such test animals 
may die within two or three weeks after the development of 
symptoms. Again they may develop the chronic type of the 
disease in the very beginning. Such cases run a rather long 
course before developing more manifest symptoms of the disease 
than periodical rises in temperature. 

When obtainable, a definite history of a previous attack of 
infectious anemia in a suspected carrier, is, for practical purposes, 
sufficient to incriminate the animal. 



OEGANISMS PATHOGENIC FOR LOWER ANIMALS ONLY 173 

In view of the fact that carriers of the virus of infectious anemia, 
besides menacing the health of other horses, almost invariably 
suffer relapses which finally terminate fatally, they should be 
promptly destroyed and the carcasses properly disposed of. 

2. The virus of contagious pleuro-pneumonia of cattle 
("Asterococcus mycoides") 

Contagious pleuro-pneumonia of cattle is an acute, subacute, 
and occasionally chronic, disease of cattle, characterized by exu- 
dative inflammation of the interlobular lymph vessels and alveolar 
tissue of the lungs, with a sero-fibrinous pleurisy. 

The disease at present does not exist in the United States, the 
last case in this country being destroyed in 1892. This scourge, 
however, has made its appearance in the United States several 
times and has been eradicated only through energetic efforts of 
the federal Department of Agriculture in cooperation with the 
authorities in the states involved. During 1886, in the state of 
Illinois alone, approximately 10,000 cattle were affected with the 
disease. 

Contagious pleuro-pneumonia is caused by a very minute virus 
which will pass the Berkefeld filter and the Chamberland cylinder 
of "F" porosity, but is held back by the Chamberland "B" filter. 
It is possible to cultivate the organism artificially in Martin's 
bouillon containing beef serum, and also in several other types of 
serum media. When magnified approximately 1500 diameters 
with considerable illumination, the organisms are seen as poly- 
morphic bodies, appearing as minute refracting dots, very short 
spirillae, and branching and asteroid figures. Borrel (47) and 
his associates in studying the pleomorphic nature of the organism 
observed coccic, streptococcic and morula-shaped forms, as well 
as short, spiral threads, showing fork-shaped branchings, and 
asteroid and mycelioid bodies, surrounded with a fine mucin cover- 
ing. Because of these findings he termed the organism "Astero- 
coccus mycoides." 

Animals which have apparently recovered from contagious 
pleuro-pneumonia have been known to harbor and transmit the 
virus to healthy animals several months to two or three years 
subsequently. The great percentage of such recoveries, however, 
are more apparent than real as relapses in arrested cases usually 



174 CARRIERS IN INFECTIOUS DISEASES 

occur. The majority of these carriers, therefore, come in the 
category of "relapsing carriers." 

Habitat of the virus. The virus of contagious pleuro-pneumonia 
is usually found in sequestrated and encapsulated lesions in the 
lungs of animals which harbor the infection following apparent 
recovery. 

Autopsy of such animals reveals in one or both lungs, a single, 
rarely several, so-called "sequesters." In these lesions areas of 
the lobular tissue have undergone necrosis. The necrotic portion 
is surrounded by a dense connective tissue capsule, the necrotic 
piece lying free (occasionally partly adherent) in the cavity thus 
formed. This necrotic piece, in cases which are not of too long 
standing, consists of a soft, mushy, outer portion and a rather 
firm inner part, which on section appears mottled. In long- 
standing cases this tissue breaks down, forming a thick, greasy, 
pasty mass. When such lesions are comparatively small they may 
gradually become absorbed. In a large percentage of cases, 
however, the process subsequently breaks through the limiting 
capsule, giving rise to a recurrence of the acute condition, with 
spread of the infection. When these "sequesters" are entirely 
closed by the connective tissue capsule the virus in the lesion is 
held in such locality. However, when they communicate with 
a bronchus infectious material is more or less continuously 
expelled. 

The circulating blood is not favorable for the propagation of 
the virus of contagious pleuro-pneumonia, hence, in carriers, it is 
not harbored in the blood stream. 

Detection and management. Detection of carriers of the virus of 
contagious pleuro-pneumonia is practically impossible of accom- 
plishment through examination of the suspected animal in the 
living state. History of cases of the disease associated with cer- 
tain animals, and knowledge of previous pulmonary affections in 
suspected carriers, constitute incriminating evidence. 

As no satisfactory treatment is known for contagious pleuro- 
pneumonia, and as apparently recovered animals carrying the 
virus are prone to suffer relapses, cattle shown, with a reasonable 
degree of certainty, to harbor the infection should be slaughtered. 
Definite history of a previous attack of the disease in a suspected 
carrier is ample evidence for its destruction. 



ORGANISMS PATHOGENIC FOR LOWER ANIMALS ONLY 175 

3. The virus of equine influenza 

Influenza, "pink eye" or "shipping fever/' is a common and 
important disease of the equine species. It manifests itself as an 
acute, febrile contagion, characterized by a catarrhal inflammation 
of the mucous membranes, especially those of the head region. 
Further, inflammatory or edematous swellings in various parts of 
the subcutis and the tendons are common to the affection. 

The etiology of the disease has been more or less obscure but 
in view of positive transmission experiments conducted by a 
number of investigators with filtered inoculums, it is generally 
accepted that the causative agent is a filterable virus. 

Stallions which have recovered from the disease may harbor the 
virus in their bodies and infect healthy mares through coitus 
several months or even one or two years following recovery from 
the disease. Poels (48) was able to infect healthy horses through 
intravenous injections of filtered semen from a stallion which for 
a number of months had infected mares bred to it. Basset (49) 
demonstrated the blood of a horse which had recovered from an 
artificial inoculation, to be infectious for three and one-half 
months subsequently. 

Habitat of the virus. Nothing is known regarding the habitat 
of the influenza virus in the body of carriers aside from the fact 
that, occasionally, it may be demonstrated in the blood and in 
stallions in the semen. Because of its presence in the blood it is 
undoubtedly eliminated periodically in the urine. 

Detection and management. A stallion may readily be suspected 
of being a carrier of the influenza virus when there is frequent 
history of influenza in various mares which he serves. According 
to Hutyra and Marek (50) the disease invariably develops in from 
six to nine days where infection is brought about through coitus. 
The identification of a carrier of the influenza virus, however, is 
only established by the transmission of the disease to a normal 
animal through the inoculation of blood, semen, or other specimens 
from the suspected animal. 

Animals known to harbor the influenza virus should not be 
permitted to come in contact with susceptible animals. Stallions 
shown to be carriers should not be permitted to serve mares. 



176 CARRIERS IN INFECTIOUS DISEASES 

Apparently no attention has been paid to the treatment of 
carriers, hence, there is no data available on the value of various 
drugs which might be employed with a view to eliminating the 
virus harbored by such animals. In Germany salvarsan and neo- 
salvarsan have been extensively used in the treatment of equine 
influenza and its complications with apparently good results in a 
certain percentage of cases. In carriers of the influenza virus, 
especially valuable stallions, the use of salvarsan or other arsenical 
products may be of value in destroying the infection. 

4- The virus of hog cholera 

Occasional reference is made in the literature on hog cholera, 
to possible carriers of the filterable virus of the disease among 
apparently recovered hogs. Further, the so-called "runts" which 
have had a chronic type of the affection have often been considered 
carriers of the infection. There appears, however, to be no rec- 
ords of carrier investigations in hog cholera, definitely establishing 
the existence of true carriers of the virus. 

Dorset (51) and his associates in experiments to determine 
whether or not several recovered hogs harbored the cholera virus, 
carried out exposure and inoculation tests with entirely negative 
results. 

Hog cholera has undoubtedly been transmitted to healthy 
animals by "runts." From present information, however, it 
appears that when such animals are capable of disseminating the 
infection they are more likely to be actually suffering from the 
chronic form of the disease than harboring the virus as carriers. 

While it is entirely possible that there are instances of real 
carriers of the hog cholera virus, at present we are without infor- 
mation on the subject. 



CHAPTER XX 
Conclusion 

There exist among animals carriers of organisms of infectious 
diseases just as they are found among members of the human 
family. The problem in veterinary medicine, however, differs 
in many respects from that in human medicine. 

As in the case of man, carriers among animals disseminate in- 
fection through their respiratory, intestinal and genito-urinary 
tracts, and indirectly through insects, but in addition we have 
milch animals harboring and eliminating organisms from their 
udders. Further, with food-producing animals the carrier problem 
does not always end with the death of the animal. Harbored 
organisms may be transmitted to man through meat or meat-food 
products. 

Under natural conditions animals are obviously more intimately 
associated than human individuals, affording conditions under 
which the carrier functions most effectively. Then the scavenging 
propensities of various species promote the carrier problem. 
Hogs, various wild animals and buzzards, for example, are con- 
tinually ingesting a vast variety of organisms, a number of which 
may persist in the intestinal tracts of such animals for variable 
periods of time, thus serving as a source of infection for susceptible 
species. 

The large number of species of animals with marked variation 
in susceptibility to certain infectious diseases, often permits 
members of one species to serve as reservoirs of infection for ani- 
mals of a more susceptible species. This is well illustrated in 
trypanosomiasis . 

In carrier work in veterinary medicine an outstanding feature 
is the fact that serological tests can, in a number of instances, be 
employed to good advantage. While such tests may not differ- 
entiate the carrier from the case, and may miss some carriers, 
nevertheless in numerous cases these tests will narrow the problem 

177 



178 CARRIERS IN INFECTIOUS DISEASES 

by identifying animals which are then, or have previously been, 
infected with a particular type of organism. 

A notable feature of the carrier problem in veterinary medicine 
is the vast number of carriers in certain of the infectious diseases. 
In bovine piroplasmosis, for example, the great percentage of 
cattle in infected districts are, or have been, carriers. 

In the control of carriers among veterinary subjects ability to 
slaughter animals harboring pathogenic organisms, where such 
procedure is feasible, is a distinct advantage. In addition, control 
is more perfect because the personal element is largely eliminated. 

LITERATURE CITED 

(1) Zammit: Report, English Commission on Malta Fever, 1905-07. 

(2) Mohler and Hart: Annual Report, Chief, U. S. Bureau of Animal 

Industry, 1908. 

(3) Saisawa : Zeitschrif t f ur Hygiene und Infektionskrankheiten, Leipzig, 

1912, lxx, 177. 

(4) Evans, Alice C. : Jour. Infectious Diseases, 1918, xxii, 580. 

(5) Annual Report, Chief, U. S. Bureau of Animal Industry, 1921. 

(6) Mohler and Buckley: Annual Report, Chief, U. S. Bureau of 

Animal Industry, 1902. 

(7) O'Brien: X. P., 231 (1910). 

(8) Heuser: Zeitschrif t fur Hygiene und Infektionskrankheiten, Leipzig, 

1910, lxv, 8. 

(9) Zwick and Weichel: Ibid., xxxviii, 1911, 327. 

(10) Meissner, Berge and Kohlstock: Centralblatt fur Bakteriologie, 

Parasitenkunde und Infektionskrankheiten, 1912, 1 Abt., Orig., 
lxv, 38. 

(11) Savage, W. G. : Food Poisoning and Food Infections. University 

Press, Cambridge, England, 1920. 

(12) Park and Williams: Pathogenic Microorganisms. Lea & Febiger, 

New York, and Philadelphia, 1917. 

(13) Savage, W. G. : Cats and Human Diphtheria. Jour, of Hygiene, 

xviii, no. 4, February, 1920. 

(14) Simmons, J. S. : Virulent Diphtheria Bacilli Carried by Cats. Amer. 

Jour. Med. Sci., clx, no. 4, October, 1920, pp. 589. 

(15) Indian Plague Commission: The Existence of Chronic Plague in Rats 

in Localities Where Plague is Endemic. Jour. Hyg., vi, no. 4, 
Extra "Plague Number," September, 1906. 

(16) McCoy, G. W. : U. S. Public Health Bulletin No. 43, U. S. Public 

Health and Marine Hospital Service, April, 1911. 

(17) McCoy and Chapin: Jour. Infec. Dis., x, 1912. 

(18) Lubowsky: Deutsche medizinische Wochenschrift (Berlin), 1910, 116. 



CONCLUSION 179 

(19) Olt: Sur la Presence Reguliere du Bacille du Rouget dans Tintestin 

du Pore. Jour, de Med. Veterinaire, April, 1901. 

(20) Pitt: Cited from Special Pathology and Therapeutics of the Diseases 

of the Domestic Animals. Hutyra and Marek, English trans., 
1916, vol. 1. 

(21) Sergent, Lombard and Quilichina: Cited from Special Pathology 

and Therapeutics of the Diseases of the Domestic Animals. 
Hutyra and Marek, vol. 1, pp. 906, 1916. 

(22) Bussenius and Siegel: Deutsche medizinische Wochenschrift, 

Berlin, 1896-97. 

(23) Zschokke: Cited from Special Pathology and Therapeutics of the 

Diseases of the Domestic Animals. Hutyra and Marek, English 
trans., vol. 1, pp. 362, 1916. 

(24) Bang : Cited from Special Pathology and Therapeutics of the Diseases 

of the Domestic Animals. Hutyra and Marek, English trans., 
vol. 1, pp. 356, 1916. 

(25) Loeffler: Cited from Moore, Jour, of the A. V. M. A., vol. 1, no. 4, 

1916. 

(26) Mohler: Foot-and-mouth Disease with Special Reference to the Out- 

break of 1914-15. Jour, of the A. V. M. A., vol. 1, no. 4, January, 
1916. 

(27) Schroeder: Bureau of Animal Industry Investigation on Bovine 

Infectious Abortion. Jour, of the A. V. M. A., vol. 13, no. 5, 
February, 1922. 

(28) Mohler and Traum: Infectious Abortion of Cattle. Bureau of 

Animal Industry Circular No. 216, 1913. 

(29) Larsen and Sedgwick: 7th Annual Report of the American Associa- 

tion of Medical Milk Commissions, 1913. 

(30) Cooledge, L. H. : Is Bacterium abortus Pathogenic for Human 

Beings? Jour, of Medical Research, xxxiv, 459, 1916. 

(31) Buck, Creech and Ladson: Bacterium abortus Infection of Bulls. 

Jour, of Agricultural Research, xvii, no. 5, August 15, 1919. 

(32) Huddleson: The Isolation of Bacterium abortus from Milk. Mich. 

Agric. Col. Exper. Sta. Technical Bull. No. 49, November, 1920. 

(33) Laveran and Mesnil: Trypanosomiasis and Trypanosomes. Lon- 

don, 1907. 

(34) Hutyra and Marek: Special Pathology and Therapeutics of the 

Diseases of Domestic Animals. English trans., vol. 1, pp. 866, 
1916. 

(35) Bruce: Cited from Special Pathology and Therapeutics of the Dis- 

eases of the Domestic Animals. Hutyra and Marek, English 
trans., vol. 1, pp. 904, 1916. 

(36) Thomas and Breinl: Cited from Trypanosomiasis and Trypano- 

somes. Laveran and Mesnil, London, 1907. 

(37) Eichhorn and Gallagher: Spontaneous Amebic Dysentery in 

Monkeys. Jour, of Infectious Diseases, xix, no. 3, September, 
1916. 



180 CARRIERS IN INFECTIOUS DISEASES 

(38) Moore, V. A.: Pathology and Differential Diagnosis of Infectious 

Diseases of Animals. 4th ed., 1916, Macmillan Co., New York. 

(39) Manninger: The Significance of the Bacilli Carrier with Regard to 

the Spread of Fowl Cholera. Allatorvosi Lapak, 1921, s. 3. 
Abst. by Marek in Deut. Tierarzt. Wchnschr., 1921, p. 537. 

(40) Hastings, Beach and Had ley: The Detection of Johne's Disease 

by the Use of Johnin. Jour, of the A. V. M. A., v, no. 4, Jan- 
uary, 1918. 

(41) Bang: Enteritis Chronica Paratuberculosa Bovis. Berliner Tier- 

arztliche Wochenschrift, 5 u. 54, 1911. 

(42) Gage: Notes on Ovarian Infection with Bacterium pullorum in the 

Domestic Fowl. Jour. Med. Res., 1911, xxiv, 491. 

(43) Jones: The Value of the Macroscopic Agglutination Test in Detecting 

Fowls that are Harboring Bacterium pullorum. N. Y. State 
Veterinary College Report, 1911-12, pp. 149. 

(44) Rettger, Kirkpatrick, and Jones: Bacillary White Diarrhea of 

Young Chicks. Bull. No. 77, Storrs Agric. Exp. Sta., June, 1914. 

(45) Schroeder and Cotton: Personal communication. 

(46) Nuttall and Strickland : Centralblatt fur Bakteriologie. Para- 

sitenkunde und Infektionskrankheiten, 1910, lvi, 524. 

(47) Borrel Dujardin-Beattmetz, Jeantet and Jouan: Ibid., 168. 

(48) Poels: Cited from Special Pathology and Therapeutics of the 

Diseases of Domestic Animals. Hutyra and Marek, English 
trans., vol. 1, pp. 183, 1916. 

(49) Basset: Comptes rendus des seances de PAcademic des Sciences 

(Paris), 1911, cliii, 485. 

(50) Hutyra and Marek : Special Pathology of the Diseases of the Domes- 

tic Animals. English trans., vol. 1, pp. 185, 1916. 

(51) Dorset, McBride, Niles and Rietz: Investigations Concerning 

the Sources and Channels of Infection in Hog Cholera. Jour. 
Agric. Research, xiii, no. 2, April 8, 1918. 



INDEX 



Abortion, bovine, infectious, car- 
riers among cattle, 153 

Alimentary diseases, 43 

Amoebiasis, human, 66 
carriers among fowls, 160 
carriers among monkeys, 160 

Anthrax, carriers among hogs, 135 

Anemia, infectious, equine, car- 
riers of virus among horses, 171 

Aphthous fever, carriers among 
cattle, 147 

Applicants, examination of, 115 

Asterococcus mycoides, 173 
see pleuro-pneumonia, conta- 
gious, cattle, 173 



Bacterium abortus (Bang), carriers 
among cattle, 153 

Bacillus aerogenes capsulatus, 
carriers among animals, 143, 144 

Bacillus aertrycke, carriers among 
animals, 129 

Bacillus anthracis, carriers among 
hogs, 135 

Bacillus bipolaris septicus, carriers 
among animals, 161 

Bacillus botulinus, carriers among 
animals, 143, 144 

Bacillus coli, carriers among ani- 
mals, 143, 144 

Bacillus diphtheriae, carriers among 
animals, 137 

Bacillus enteritidis (Gaertner), car- 
riers among animals, 129 

Bacillus erysipelatis suis, carriers 
among hogs, 141 



Bacillus lactis aerogenes, carriers 

among animals, 144 
Bacillus mallei, carriers among 

horses, 136 
Bacillus necrophorus, carriers 

among animals, 162 
Bacillus oedematis maligni, car- 
riers among animals, 134 
Bacillus paratuberculosis, carriers 

among cattle, 164 
Bacillus paratyphosus, 45 

carriers among animals, 129 
Bacillus pestis, carriers among rats 

and squirrels, 139 
Bacillus phegmasis uberis, carriers 

among animals, 144 
Bacillus prOteus mirabilis, carriers 

among animals, 144 
Bacillus pyocyaneus, carriers 

among animals, 143, 144 
Bacillus pyogenes, carriers among 

animals, 143, 144 
Bacillus suipestifer, carriers among 

animals, 129 
Bacillus tetani, carriers among 

animals, 132 
Bacillus tuberculosis, 99, 125 
carriers among cattle, 126 
carriers among hogs, 127 
Bacteria, animal carriers of bac- 
terium pullorum, 6, 123, 151, 161 
carriers among fowls, 166 
Bacterium tularense, carriers 

among squirrels and rabbits, 140 
Balantidium coli, carriers among 

hogs, 160 
Balantidiosis, human, 69 
Blood group of diseases, 44 



181 



182 



INDEX 



Cats, carriers of B. diphtheriae, 137 
carriers of miscellaneous bac- 
teria, 143 
Cattle, carriers of B. bipolaris 
septicus, 160 
carriers of B. oedematis ma- 

ligni, 134 
carriers of B. paratuberculo- 

sis, 164 
carriers of B. tetani, 132 
carriers of B. tuberculosis, 126 
carriers of Bact. abortus (Bang), 

153 
carriers of miscellaneous bac- 
teria, 143 
carriers of organisms of Sal- 
monella group, 129 
carriers of piroplasmata, 167 
carriers of streptococcus of bovine 

mastitis, 151 
carriers of virus of contagious 

pleuro-pneumonia, 173 
carriers of virus of foot-and- 
mouth disease, 147 
Cholecystitis, 29, 48, 56, 131 
Cholera, 60 

Cholera, hog carriers, 176 
Classification, 15 

Coccidia, carriers among ani- 
mals, 160 

D 

Dermatitis, gangrenous, equine, 162 
Diarrhea, white, of fowls, 166 
Diphtheria, 72 

carriers among animals, 137 
Dogs, carriers of Leishmania 
canis, 145 

carriers of miscellaneous bac- 
teria, 143 
Dourine, animal carriers, 158 
Duodenal contents, 51 
Dysentery, amoebic, 66 

bacillary, 64 



E 

Enteriditis group of organisms, see 

Salmonella group 129 
Enteritis, paratuberculous, bovine, 

164 

bovine, 164 
Erysipelas, swine, 141 



Filariasis, 103 
Filterable viruses, 100 

animal carriers of, 147, 171 
Food handlers, 115 
Foot-and-mouth disease, 115 

carriers among cattle, 147 
Foot-rot of sheep, 162 
Fowls, carriers of amoebae, 160 

carriers of B. bipolaris sep- 
ticus, 161 

carriers oiB. pullorum, 166 

G 

Gaertner group, see Salmonella 

group, 129 
Glanders, carriers among horses, 136 
Goats, carriers of M. melitensis, 123 
Gonorrhoea, 106 

Guinea pigs, carriers of B. 
aertrycke, 129 
carriers of B. suipestifer, 129 
carriers of B. tetani, 132 

H 

Helminthoses, 70 

Hemorrhagic septicemia group, 
animal carriers, 161 

Hogs, carriers of B. anthracis, 135 
carries of B. bipolaris septicus 161 
carriers of B. botulinus, 144 
carriers of B. erysipelatis suis, 141 
carriers of B. necrophorus, 162 
carriers of B. oedematis ma- 

ligni, 134 
carriers of B. tetani, 132 
carriers of B. tuberculosis, 127 



INDEX 



183 



Hogs, — Continued . 

carriers of Balantidium coli, 160 
carriers of miscellaneous bac- 
teria, 143 
carriers of organisms of Sal- 
monella group, 129 
Hookworm disease, 70 
Horses, carriers of B. bipolaris 
septicus, 161 
carriers of B. mallei, 136 
carriers of B. edematis ma- 

ligni, 134 
carriers of B. tetani, 132 
carriers of miscellaneous bac- 
teria, 143 
carriers of Nuttallia equi, 170 
carriers of piroplasma, 170 
carriers of virus of equine in- 
fluenza, 175 
carriers of virus of infectious 
anemia, 171 
Hygiene, 112 

I 

Influenza bacillus, 97 
Influenza, equine carriers of virus 
among horses, 175 



Johne's Disease in cattle, carriers 
of, 164 

K 
Kala-azar in dogs, carriers, 145 
L 

Laboratory work, 34 

Leishmania canis, carriers among 
dogs, 145 

Leishmaniasis, canine, see Leish- 
mania canis, 145 

Lip-and-leg ulceration of sheep, 162 

M 

Malaria, 101 

Mai de caderas of horses, 157 



Malta fever in goats, see M. meli- 

tensis, 123 
Mastitis, bovine, infectious, see 

Strep, of bovine mastitis, 151 
Meningitis, 79 
Mice, carriers of organisms of 

Salmonella group, 130 
Military services, 116 
Miscellaneous bacteria carried by 

animals, 143 
Monographs, 5 

N 

Nagana in animals, 157 
Nuttallia equi, 170 



Paratyphoid group, see Salmonella 

group, 129 
Phorology, 14 

Physical examinations, 116 
Piroplasma caballi, carriers among 

horses, 170 
Piroplasmata bigeminum and bovis, 

carriers among cattle, 167 
Piroplasmosis of cattle, 167 
Piroplasmosis of horses, 170 
Plague, bubonic, carriers among 

rats and squirrels, 139 
Pneumonia, 87 
Preventive medicine, 111 
Protozoa, animal carriers of 145, 

156, 159, 167 
Pyelitis, 33, 49 

R 

Rabbits, carriers of B. tetani, 133 
carriers of Bact. tularense, 141 

Rats, carriers organisms of Salmon- 
ella group, 130 
carriers, of B. pestis, 139 

Records, 118 

Recruits, 117 

Red-water, British, of cattle, 167 

Respiratory diseases, 44 



184 



INDEX 



Rodents, carriers organisms 

Salmonella group, 130 
Rules of hygiene, 113 



of 



Salmonella group of organisms, 129 

carriers among animals, 129 
Sanitation, 111 
Sexual diseases, 44, 114 
Sheep, carriers of B. oedematis 
maligni, 134 
carriers of B. tetani, 132 
carriers of miscellaneous bac- 
teria, 143 
Specimens of feces, 51 
Specimens from nasopharynx, 82 
Squirrels, carriers of B. pestis, 139 

carriers of Bact. tularense, 140 
Staphylococci, carriers among ani- 
mals, 143 
Streptococcus, of bovine infectious 
mastitis, 151 
carriers among cattle, 151 



Streptococci, 90 

carriers among animals, 143 
Surra, carriers among animals, 157 
Syphilis, 104 

T 

Tetanus, animal carriers, 132 
Texas fever of cattle, 167 
Tonsillitis, 26, 74 
Trypanosoma, Brucei, 157 

equinum, 157 

equiperdum, 157 

Evansi, 157 
Trypanosomiasis, animal carriers, 

156 
Tuberculosis, 99, 125 
Tularemia, 140 
Typhoid, 45 

V 

Vaccination, 113 

Veterinary medicine, carriers in, 121 

conclusion to section on, 177 
Vibrion septique, animal car- 
riers, 134 
Vincent's angina, 98 






